Meta tags:
author=Gwern;
description=Compilation of studies comparing observational results with randomized experimental results on the same intervention, compiled from medicine/economics/psychology, indicating that a large fraction of the time (although probably not a majority) correlation ≠ causality.;
keywords=economics, insight-porn, psychology/cognitive-bias, statistics/bayes/regression-to-mean, statistics/bias, statistics/causality;

Headings (most frequently used words):

how, often, does, correlation, causality, medical, economics, sociology, psychology, education, todo, backlinks, similar, links, bibliography,

Text of the page (most frequently used words):
the (1183), and (575), for (318), studies (247), that (211), randomized (202), from (150), estimates (147), were (142), with (134), results (115), non (108), was (105), experimental (102), are (90), between (86), effects (85), this (82), observational (80), not (78), trials (76), estimate (76), effect (71), nonexperimental (71), treatment (69), than (69), table (64), data (63), these (62), control (61), meta (60), study (60), outcomes (58), group (57), which (55), comparisons (54), impact (52), program (51), have (50), our (50), other (47), but (47), nonrandomized (47), comparison (46), bias (46), differences (46), two (46), difference (46), more (45), they (44), analysis (43), different (43), significant (43), all (42), risk (41), there (39), each (37), design (37), size (37), reviews (37), had (36), evidence (34), use (34), been (34), school (34), used (33), relative (33), average (33), one (33), controlled (33), across (32), assignment (31), would (31), compared (31), interventions (31), earnings (31), health (30), also (30), using (30), may (30), spending (30), medical (30), rcts (30), clinical (29), experiments (29), only (29), significantly (29), intervention (29), participants (29), research (28), same (28), groups (28), both (27), reported (27), trial (27), random (26), test (26), large (26), selection (26), review (25), class (25), some (25), analyses (25), did (25), confidence (24), assigned (24), included (24), mean (24), teacher (23), those (23), estimated (23), scores (23), found (23), statistically (23), case (23), training (22), programs (22), methods (22), can (22), findings (22), standard (22), experiment (22), based (22), example (22), within (22), therapy (21), outcome (21), characteristics (21), who (21), such (21), similar (20), student (20), out (20), among (20), over (20), first (20), population (20), plan (20), topic (19), sizes (19), systematic (19), cancer (19), students (19), about (19), how (19), could (19), into (19), evaluation (18), prior (18), regression (18), their (18), randomly (18), when (18), four (18), larger (18), published (18), measures (17), small (17), smaller (17), column (17), topics (17), showed (17), many (16), performance (16), classes (16), however (16), higher (16), points (16), score (16), level (16), cost (16), association (16), new (15), self (15), increase (15), high (15), quality (15), even (15), after (15), rct (15), absolute (15), percentage (15), adjustment (15), odds (15), adjusted (15), most (15), estimators (15), confounding (15), cohort (15), employment (14), disease (14), greater (14), very (14), where (14), close (14), low (14), total (14), well (14), lift (14), has (14), reduction (14), project (14), whether (14), children (14), trainees (14), related (13), work (13), point (13), variables (13), any (13), associated (13), consistent (13), find (13), estimator (13), true (13), method (13), figure (13), primary (13), cases (13), considered (13), ratio (13), unbiased (13), star (13), literature (13), schools (13), regular (13), interval (13), cited (13), mortality (13), harms (13), evaluating (12), effectiveness (12), designs (12), teachers (12), panel (12), likely (12), without (12), three (12), often (12), summary (12), conclusion (12), direction (12), second (12), pre (12), rcd (12), what (11), efficacy (11), welfare (11), intervals (11), important (11), sample (11), achievement (11), include (11), result (11), columns (11), compare (11), comparing (11), show (11), least (11), because (11), areas (11), made (11), statistical (11), significance (11), set (11), type (11), criterion (11), effective (11), assess (11), wellness (11), plans (11), highly (11), psychological (10), lipsey (10), wilson (10), causal (10), evaluations (10), 2002 (10), including (10), randomization (10), less (10), variable (10), education (10), while (10), heterogeneity (10), lower (10), during (10), deviation (10), row (10), surgery (10), selected (10), types (10), noted (10), per (10), might (10), area (10), overall (10), shows (10), empirical (10), patients (10), five (10), factors (10), employees (10), claims (10), six (10), nsw (10), breast (10), further (9), 24ya (9), cardiovascular (9), math (9), magnitude (9), suggest (9), ols (9), controls (9), researchers (9), should (9), matching (9), behaviors (9), consider (9), measure (9), variation (9), common (9), conclusions (9), available (9), risks (9), differed (9), treatments (9), eight (9), range (9), post (9), previous (9), concluded (9), led (9), differ (9), benefit (9), being (9), several (9), tested (9), workers (9), absenteeism (9), workplace (9), poverty (9), contradicted (9), load (8), 1998 (8), epidemiological (8), information (8), although (8), rule (8), following (8), 2013 (8), models (8), years (8), time (8), see (8), much (8), decision (8), 2018 (8), given (8), before (8), issue (8), identified (8), drug (8), procedure (8), gain (8), statistic (8), features (8), pairs (8), 100 (8), potential (8), year (8), participation (8), sites (8), job (8), energy (8), male (8), colleagues (8), model (7), 1983 (7), educational (7), 1987 (7), coaching (7), 1990 (7), 1999 (7), 27ya (7), social (7), 28ya (7), generally (7), conducted (7), calculated (7), through (7), versus (7), interest (7), still (7), people (7), demand (7), question (7), approaches (7), hypothesis (7), propensity (7), examine (7), contrast (7), searched (7), 1986 (7), particular (7), patient (7), subjects (7), positive (7), subsequent (7), number (7), criteria (7), provide (7), enough (7), benefits (7), 1988 (7), drawn (7), possible (7), shown (7), expenditures (7), cause (7), assessed (7), rates (7), against (7), care (7), approach (7), importance (7), baseline (7), jones (7), individual (7), divorce (7), residual (7), enrollee (7), oral (7), stronger (7), intake (7), links (6), error (6), shapiro (6), psychology (6), 1993 (6), family (6), therapies (6), 39ya (6), 2000 (6), 26ya (6), prevention (6), current (6), validity (6), indicating (6), errors (6), cross (6), though (6), comes (6), demographic (6), report (6), its (6), days (6), terms (6), run (6), since (6), key (6), just (6), received (6), better (6), tests (6), surgical (6), ratios (6), 40ya (6), prospective (6), chance (6), ioannidis (6), standardized (6), 000 (6), ability (6), yielded (6), present (6), authors (6), university (6), paper (6), does (6), papers (6), 38ya (6), pooled (6), quite (6), inferences (6), whereas (6), percentile (6), appendix (6), then (6), therefore (6), collected (6), age (6), status (6), addition (6), assessment (6), impacts (6), female (6), participate (6), women (6), rate (6), worksites (6), itt (6), eligible (6), econometric (6), degree (6), economics (6), females (6), members (6), specific (6), birth (6), multiple (6), death (6), initially (6), analysed (6), kunz (6), tools (6), exposure (6), smoking (6), suicide (6), innovation (6), backlinks (5), 43ya (5), journal (5), methodological (5), behavioral (5), 33ya (5), 36ya (5), maclehose (5), vitamin (5), role (5), contain (5), content (5), indicates (5), 2017 (5), precision (5), treated (5), few (5), separate (5), fixed (5), beyond (5), surveys (5), give (5), period (5), hours (5), sectional (5), factor (5), vary (5), individuals (5), long (5), relevant (5), advertising (5), due (5), million (5), produced (5), evaluated (5), checkout (5), leads (5), precise (5), way (5), equal (5), specification (5), obtained (5), adjustments (5), cochrane (5), separately (5), good (5), correlation (5), fold (5), performed (5), 2001 (5), zero (5), unpublished (5), ones (5), failure (5), single (5), wrong (5), his (5), krueger (5), background (5), them (5), measured (5), sets (5), negative (5), above (5), testing (5), major (5), procedures (5), food (5), implemented (5), 2016 (5), setting (5), correlational (5), nearly (5), existing (5), tables (5), restricted (5), annual (5), comprehensive (5), eligibility (5), plausible (5), fig (5), substantial (5), replicate (5), young (5), examined (5), crime (5), moving (5), families (5), housing (5), step (5), cps (5), ssa (5), econometricians (5), populations (5), afdc (5), supported (5), hypertension (5), syntheses (5), claim (5), bleed (5), coronary (5), acute (5), journals (5), lead (5), searches (5), britton (5), prognostic (5), calcium (5), hcts (5), causality (5), associations (5), contraceptives (5), day (4), bibliography (4), page (4), bulletin (4), comparative (4), implications (4), american (4), becker (4), scholastic (4), aptitude (4), synthesis (4), commonly (4), demonstration (4), match (4), policy (4), derived (4), potentially (4), despite (4), relatively (4), allows (4), others (4), fact (4), classroom (4), corresponding (4), predicted (4), behavior (4), questions (4), indicate (4), decisions (4), value (4), observations (4), suggests (4), generated (4), investigate (4), field (4), like (4), exact (4), reject (4), reports (4), answer (4), conversion (4), exposed (4), matched (4), produce (4), gave (4), digestive (4), discrepancies (4), databases (4), original (4), combined (4), 2004 (4), 22ya (4), alone (4), publication (4), natural (4), 25ya (4), yield (4), values (4), attrition (4), interaction (4), means (4), grouping (4), differential (4), take (4), main (4), variance (4), problem (4), secondary (4), kinds (4), almost (4), recent (4), compares (4), activity (4), either (4), provides (4), third (4), seven (4), thus (4), calculations (4), reduce (4), states (4), divided (4), kindergarten (4), determine (4), extent (4), basis (4), assessing (4), tennessee (4), problems (4), distribution (4), 1989 (4), 37ya (4), ways (4), lalonde (4), focused (4), carried (4), wilde (4), hollister (4), 2007 (4), nonparticipants (4), collection (4), rather (4), administrative (4), song (4), baicker (4), employee (4), frequently (4), visits (4), under (4), survey (4), screening (4), discrepancy (4), roi (4), 2010 (4), 16ya (4), change (4), patterns (4), appear (4), households (4), state (4), ates (4), double (4), readiness (4), mto (4), experimentally (4), ludwig (4), gender (4), proportion (4), developmental (4), variability (4), life (4), usually (4), whose (4), psid (4), enrollees (4), expected (4), 2014 (4), prevent (4), chronic (4), fractures (4), cereal (4), process (4), supplementation (4), myocardial (4), infarction (4), improved (4), adverse (4), increased (4), decrease (4), benson (4), concato (4), investigated (4), oxman (4), sacks (4), mix (4), situations (4), diet (4), recall (4), men (4), cigarettes (4), site (3), require (3), javascript (3), hedges (3), confirmation (3), hazelrigg (3), dehejia (3), wahba (3), friedlander (3), robins (3), 1995 (3), fraker (3), maynard (3), bloom (3), michalopoulos (3), hill (3), lei (3), york (3), manpower (3), corporation (3), glazerman (3), supplement (3), todo (3), relationship (3), happiness (3), degrees (3), around (3), generate (3), instrumental (3), calculate (3), instead (3), account (3), moved (3), 2008 (3), 18ya (3), independent (3), reading (3), policymakers (3), identifying (3), remain (3), capture (3), unique (3), development (3), controlling (3), techniques (3), unobservable (3), advertiser (3), overestimate (3), approximately (3), properly (3), listeners (3), sense (3), absence (3), said (3), ask (3), hence (3), metrics (3), truth (3), top (3), half (3), exposures (3), fail (3), fourth (3), seen (3), articles (3), equivalent (3), calculation (3), 2006 (3), 20ya (3), observed (3), tended (3), frequent (3), discrepant (3), varied (3), ideal (3), allowed (3), computation (3), pretest (3), conditions (3), specifically (3), cell (3), lowest (3), highest (3), sat (3), presurgical (3), put (3), mechanism (3), substantive (3), considerably (3), component (3), nonrandom (3), inclusion (3), aggregated (3), detail (3), statistics (3), extremely (3), past (3), choosing (3), suggested (3), smith (3), entire (3), reproduce (3), maybe (3), glass (3), 1980 (3), 46ya (3), colditz (3), miller (3), inconsistent (3), strong (3), considerable (3), theory (3), analysts (3), closely (3), except (3), classrooms (3), raw (3), answers (3), crucial (3), always (3), levels (3), providing (3), sign (3), ranging (3), usual (3), sometimes (3), entry (3), developed (3), increases (3), future (3), gains (3), uses (3), reducing (3), experience (3), slightly (3), somewhat (3), sufficient (3), indeed (3), misleading (3), invest (3), opposite (3), situation (3), cutoff (3), another (3), presents (3), sex (3), race (3), free (3), aide (3), principal (3), occurred (3), course (3), deviations (3), source (3), utilization (3), reliable (3), applied (3), provided (3), focus (3), sociology (3), full (3), probability (3), introduced (3), weight (3), markers (3), blood (3), pressure (3), domains (3), moreover (3), rules (3), lies (3), campus (3), gym (3), rich (3), particularly (3), biases (3), described (3), left (3), plots (3), expressed (3), tot (3), along (3), return (3), widely (3), savings (3), cutler (3), additional (3), 2011 (3), 15ya (3), productivity (3), event (3), simple (3), records (3), studied (3), yet (3), support (3), designed (3), 19ya (3), utilities (3), department (3), affects (3), affect (3), accounting (3), documented (3), occasionally (3), center (3), mothers (3), scale (3), 259 (3), crimes (3), violent (3), neighborhood (3), preprogram (3), offered (3), mobility (3), essentially (3), duncan (3), income (3), mental (3), will (3), unlike (3), tend (3), histories (3), unadjusted (3), ten (3), target (3), bar (3), corresponds (3), medicaid (3), reduced (3), similarly (3), 12ya (3), objective (3), routinely (3), making (3), 275 (3), sources (3), concordant (3), chemicals (3), bpa (3), search (3), 133 (3), items (3), scientific (3), epidemiologic (3), daily (3), contradictory (3), interpretation (3), symptomatic (3), intracranial (3), anticoagulant (3), blocker (3), defined (3), medline (3), striking (3), botulinum (3), toxin (3), dinoprostone (3), mechanical (3), ventilation (3), according (3), quasi (3), concurrent (3), heart (3), instances (3), hartz (3), allocated (3), methodology (3), historical (3), epidemiology (3), technique (3), allocation (3), blinding (3), lung (3), spurious (3), evident (3), saturated (3), fat (3), hiv (3), beta (3), carotene (3), bhat (3), mann (3), whitney (3), blind (3), public (2), service (2), annotation (2), hairsp (2), feedback (2), references (2), here (2), enabled (2), disabled (2), 388 (2), 395 (2), consulting (2), 1181 (2), 1209 (2), psychologist (2), cooper (2), borduin (2), 101 (2), 428 (2), 442 (2), integrative (2), 373 (2), 417 (2), appraisal (2), 31ya (2), adequacy (2), mandatory (2), levy (2), myers (2), washington (2), mathematica (2), replications (2), reeves (2), harvey (2), sheldon (2), white (2), 1997 (2), 29ya (2), causes (2), antioxidant (2), vitamins (2), imply (2), moderate (2), distinguish (2), shrunken (2), bacher (2), hicks (2), explanation (2), estimation (2), strongly (2), kane (2), 13ya (2), describing (2), order (2), skills (2), caution (2), appropriate (2), stakes (2), allow (2), month (2), closer (2), overestimates (2), width (2), improvement (2), suffer (2), caused (2), known (2), sensitivity (2), endogeneity (2), economic (2), engineering (2), resources (2), done (2), naturally (2), occurring (2), got (2), ads (2), measuring (2), know (2), 117 (2), 534 (2), fails (2), section (2), registration (2), view (2), little (2), summarizes (2), pixel (2), figures (2), users (2), gold (2), facebook (2), conditioning (2), linear (2), explain (2), 2019 (2), measurement (2), big (2), pubmed (2), april (2), binary (2), extracted (2), occur (2), 009 (2), 240 (2), 168 (2), projecting (2), passive (2), internal (2), note (2), largest (2), bit (2), simply (2), takes (2), 0001 (2), regressions (2), power (2), detect (2), finding (2), components (2), disparate (2), numbers (2), impossible (2), 119 (2), describe (2), adequately (2), haphazard (2), severe (2), unit (2), contained (2), juvenile (2), psychosocial (2), pupils (2), reflect (2), allowing (2), reason (2), baltimore (2), covariate (2), book (2), archived (2), medicine (2), combine (2), pattern (2), poor (2), remains (2), efficiency (2), summarized (2), 1976 (2), 50ya (2), met (2), quasiexperimental (2), 1979 (2), 47ya (2), improve (2), juveniles (2), accuracy (2), conduct (2), discussed (2), complete (2), fifth (2), again (2), looking (2), perform (2), rural (2), city (2), easy (2), entered (2), hand (2), conclude (2), aspects (2), rough (2), illustrate (2), carefully (2), taken (2), interesting (2), justify (2), costs (2), entries (2), look (2), enter (2), yes (2), gives (2), thought (2), 135 (2), seems (2), make (2), suppose (2), represents (2), closeness (2), lunch (2), broadly (2), throughout (2), cities (2), 1985 (2), schedule (2), etc (2), adjusting (2), scored (2), grade (2), below (2), various (2), motivated (2), involving (2), estimating (2), proper (2), substantially (2), attempted (2), called (2), neither (2), nor (2), etable (2), elected (2), obtain (2), endogenous (2), additionally (2), screenings (2), 4037 (2), 4106 (2), modules (2), completed (2), months (2), exercise (2), prespecified (2), sleep (2), choices (2), cholesterol (2), index (2), pharmaceutical (2), via (2), 140 (2), 160 (2), june (2), lasso (2), monthly (2), outside (2), 011 (2), presented (2), healthier (2), line (2), play (2), specified (2), participating (2), hra (2), variants (2), equation (2), includes (2), specifications (2), variety (2), explanations (2), typical (2), illustrates (2), treat (2), changes (2), repeat (2), 115 (2), investment (2), replicated (2), drugs (2), hospital (2), popular (2), community (2), running (2), null (2), meaningfully (2), invited (2), paid (2), amounts (2), remaining (2), online (2), limited (2), participated (2), direct (2), net (2), electricity (2), weather (2), heating (2), form (2), utility (2), household (2), opower (2), respectively (2), biased (2), consistently (2), must (2), arguments (2), directly (2), easily (2), magnuson (2), mcgroder (2), increasing (2), final (2), national (2), united (2), receipt (2), basic (2), generating (2), induced (2), schooling (2), arrests (2), opportunity (2), criminal (2), dropout (2), census (2), neighborhoods (2), adjust (2), move (2), unmeasured (2), moves (2), hirschfield (2), urban (2), voucher (2), sampling (2), observable (2), influence (2), series (2), extensive (2), cherlin (2), parental (2), contrary (2), product (2), parents (2), parent (2), earlier (2), unobservables (2), seriously (2), pretraining (2), administration (2), applicants (2), payments (2), 1975 (2), 51ya (2), federally (2), sponsored (2), identical (2), mdrc (2), depending (2), worked (2), together (2), wage (2), stay (2), occupations (2), participant (2), 137 (2), arises (2), 2022 (2), investigating (2), deaths (2), nine (2), favorable (2), length (2), head (2), circumference (2), gestational (2), kidney (2), hip (2), owing (2), older (2), bisphenol (2), diabetes (2), 2009 (2), 17ya (2), assayed (2), urine (2), 1000 (2), attack (2), endpoints (2), false (2), eating (2), biological (2), breakfast (2), standards (2), principles (2), serious (2), vaccines (2), uncontrolled (2), vascular (2), visceral (2), injury (2), laparoscopic (2), open (2), repair (2), inguinal (2), hernia (2), cmaj (2), addressing (2), feasible (2), harm (2), already (2), 4000 (2), profile (2), influential (2), general (2), 129 (2), stunted (2), stimulation (2), additive (2), achieved (2), follow (2), longer (2), acetylcysteine (2), glyceryl (2), trinitrate (2), fissure (2), curing (2), fewer (2), infants (2), intermittent (2), diazepam (2), administered (2), seizures (2), virus (2), infection (2), duration (2), cladribine (2), quintile (2), incidence (2), subsequently (2), 008 (2), surrogate (2), excluded (2), cognitive (2), computed (2), library (2), leading (2), bcg (2), stroke (2), horwitz (2), showing (2), black (2), publications (2), category (2), comparable (2), immunotherapy (2), anticoagulants (2), reviewed (2), quantitative (2), protect (2), healthcare (2), adjuvant (2), investigation (2), containing (2), feature (2), meeting (2), looks (2), investigations (2), resampling (2), sixty (2), covered (2), dose (2), response (2), relation (2), link (2), formaldehyde (2), anatomists (2), pathologists (2), intermediate (2), protects (2), obvious (2), dietary (2), slope (2), amount (2), frequency (2), questionnaires (2), hour (2), transmission (2), mechanisms (2), equally (2), cannot (2), developing (2), established (2), expanded (2), relate (2), attributed (2), externally (2), record (2), sequential (2), likelihood (2), adblock, announcement, quote, send, anonymous, superseded, services, patterson, kristal, neuhouser, potter, 786, 802, lonn, yusuf, update, 957, 965, cardiol, predictive, exception, unshrunken, roughly, 084, substantively, compliance, narrowing, blocks, shrinkage, overlapping, staiger, come, actual, closest, 995, cells, dependent, attitude, listed, block, rosters, growing, practitioners, skilled, improving, leveraging, weak, correlations, bring, revealing, proceed, professional, personnel, accountability, blazar, validating, attitudes, added, best, shot, learned, active, invariant, listener, omitted, correlate, listening, timescale, matters, platform, realized, get, happen, listen, valuable, difficult, convince, makers, consumes, implement, untouched, default, excluding, huang, consumer, audio, pandora, internet, radio, precisely, 535, 661, last, summarize, want, divide, followed, tells, tracked, conversions, equals, down, fare, equality, landing, comprising, 435, user, billion, impressions, unexposed, synthetic, markets, thousands, why, industry, accurately, gordon, embase, identify, fifty, 276, 180, 1966, 60ya, shikata, 001, occasional, timing, logarithm, events, arm, synthesized, extraction, diverse, simulate, predictor, equate, reasonable, projections, assume, tailored, projection, diminished, dramatically, smallest, confounds, involve, place, 029, 000075, borderline, interactions, conceptually, finally, twice, unusually, creating, variances, 733, describes, retrieving, proved, resulted, elimination, 103, dichotomous, eliminated, reasons, implausible, posttest, drew, tobler, devine, slavin, deliberately, manuscripts, regard, practical, contacts, willing, documents, 1992, 34ya, johns, hopkins, press, followup, doesn, anything, ordered, copy, mentions, notes, coded, date, archives, anywhere, colorado, 1977, 49ya, psychotherapy, mosteller, 343, 352, analyst, metric, aggregation, trivially, underestimate, 1193, believe, ambiguity, near, mostly, silent, consistency, empirically, certain, assumptions, correlated, executed, overridden, justifies, nonequivalent, units, cook, campbell, abuse, equated, reasonably, accurate, heinsman, shadish, 1996, 30ya, experimentation, approximate, district, indication, constructing, signs, differing, pair, subset, strict, argued, couple, presenting, sketch, elements, focuses, develops, early, elementary, discounting, appropriately, purposes, necessary, took, increasingly, critical, apply, create, contains, began, considering, conclusively, definitive, distance, observer, action, decided, stringent, indicated, weaken, stringency, vice, versa, perhaps, word, chosen, distributed, originally, nonmetropolitan, towns, manchester, maryville, inner, suburban, metropolitan, knoxville, nashville, memphis, chattanooga, beginning, curriculum, theoretically, reassigned, switched, grades, unaffected, rank, stanford, career, ladder, system, contemporaneously, exogenous, interested, construct, considerations, undertake, compelling, fashion, solely, drawing, kindergartens, derive, bootstrapping, attempting, guides, greatest, emphasis, maker, trying, wider, application, framework, complex, tried, domain, nonwhite, salaried, sales, having, incorrectly, underscoring, thereby, naive, ordinary, squares, 974, 272, engaging, actively, managing, body, mass, tenure, 937, programming, comprised, nutrition, physical, stress, registered, dietitians, clustered, january, gathered, continuously, biometrics, july, august, 2015, 11ya, indistinguishable, every, marathon, 10k, 024, inside, 757, 656, assumption, contemporaneous, spirit, demonstrate, suggesting, settings, visualization, times, generates, indicator, vector, instrument, completing, variant, strata, reductions, presence, advantageous, possibility, something, competing, performing, demonstrating, none, fall, intent, ease, bottom, establish, rely, pelletier, chapman, skew, abraham, end, publicly, independently, pal, affiliated, researcher, 2012, 14ya, quantiles, subcategory, office, facilities, ruled, demonstrates, employing, 459, 834, 300, off, successfully, earned, rewards, 350, communicated, start, permitted, combines, insurance, visit, namely, novel, cover, intended, exists, employer, financial

Text of the page (random words):
interventions they did not match rcts and non randomized studies according to the intervention although they provide some information about the average findings of selected randomized and non randomized studies they did not consider whether there are differences in results of rcts and non randomized studies of the same intervention findings of the eight reviews the eight reviews have drawn conflicting conclusions 5 of the eight reviews concluded that there are differences between the results of randomized and non randomized studies in many but not all clinical areas but without there being a consistent pattern indicating systematic bias 25 26 28 34 35 one of the eight reviews found an overestimation of effects in all areas studied 27 the final two concluded that the results of randomized and non randomized studies were remarkably similar 32 33 of the two reviews that considered the relative variability of randomized and non randomized results one concluded that rcts were more consistent 34 and the other that they were less consistent 33 contradicted and initially stronger effects in highly cited clinical research ioannidis 2005 21ya 5 of 6 highly cited nonrandomized studies had been contradicted or had found stronger effects vs 9 of 39 randomized controlled trials p 0 008 matched control studies did not have a significantly different share of refuted results than highly cited studies but they included more studies with negative results similarly there is some evidence on disagreements between epidemiological studies and randomized trials 3 5 for highly cited nonrandomized studies subsequently published pertinent randomized trials and meta analyses thereof were eligible regardless of sample size nonrandomized evidence was also considered if randomized trials were not available 5 of 6 highly cited nonrandomized studies had been contradicted or had initially stronger effects while this was seen in only 9 of 39 highly cited randomized trials p 0 008 table 3 shows that trials with contradicted or initially stronger effects had significantly smaller sample sizes and tended to be older than those with replicated or unchallenged findings there were no significant differences on the type of disease the proportion of contradicted or initially stronger effects did not differ significantly across journals p 0 60 small studies using surrogate markers may also sometimes lead to erroneous clinical inferences 158 there were only 2 studies with typical surrogate markers among the highly cited studies examined herein but both were subsequently contradicted in their clinical extrapolations about the efficacy of nitric oxide 22 and hormone therapy 42 box 2 contradicted and initially stronger effects in control studies contradicted findings in a prospective cohort 91 vitamin a was inversely related to breast cancer relative risk in the highest quintile 0 84 95 confidence interval ci 0 71 0 98 and vitamin a supplementation was associated with a reduced risk p 0 03 in women at the lowest quintile group in a randomized trial 128 exploring further the retinoid breast cancer hypothesis fenretinide treatment of women with breast cancer for 5 years had no effect on the incidence of second breast malignancies a trial n 51 showed that cladribine significantly improved the clinical scores of patients with chronic progressive multiple sclerosis 119 in a larger trial of 159 patients no significant treatment effects were found for cladribine in terms of changes in clinical scores 129 initially stronger effects a trial n 28 of aerosolized ribavirin in infants receiving mechanical ventilation for severe respiratory syncytial virus infection 82 showed significant decreases in mechanical ventilation 4 9 vs 9 9 days and hospital stay 13 3 vs 15 0 days a meta analysis of 3 trials n 104 showed a decrease of only 1 8 days in the duration of mechanical ventilation and a non statistically significant decrease of 1 9 days in duration of hospitalization 130 a trial n 406 of intermittent diazepam administered during fever to prevent recurrence of febrile seizures 90 showed a significant 44 relative risk reduction in seizures the effect was smaller in other trials and the overall risk reduction was no longer formally significant 131 moreover the safety profile of diazepam was deemed unfavorable to recommend routine preventive use a case control and cohort study evaluation 92 showed that the increased risk of sudden infant death syndrome among infants who sleep prone is increased by use of natural fiber mattresses swaddling and heating in bedrooms several observational studies have been done since and they have provided inconsistent results on these interventions in particular they disagree on the possible role of overheating 132 a trial of 54 children 95 showed that the steroid budenoside significantly reduced the croup score by 2 points at 4 hours and significantly decreased readmissions by 86 a meta analysis n 3736 133 showed a significant improvement in the westley score at 6 hours 1 2 points and 12 hours 1 9 points but not at 24 hours fewer return visits and or re admissions occurred in patients treated with glucocorticoids but the relative risk reduction was only 50 95 ci 24 64 a trial n 55 showed that misprostol was as effective as dinoprostone for termination of second trimester pregnancy and was associated with fewer adverse effects than dinoprostone 96 a subsequent trial 134 showed equal efficacy but a higher rate of adverse effects with misoprostol 74 than with dinoprostone 47 a trial n 50 comparing botulinum toxin vs glyceryl trinitrate for chronic anal fissure concluded that both are effective alternatives to surgery but botulinum toxin is the more effective nonsurgical treatment 1 failure vs 9 failures with nitroglycerin 109 in a meta analysis 135 of 31 trials botulinum toxin compared with placebo showed no significant efficacy relative risk of failure 0 75 95 ci 0 32 1 77 and was also no better than glyceryl trinitrate relative risk of failure 0 48 95 ci 0 211 10 surgery was more effective than medical therapy in curing fissure relative risk of failure 0 12 95 ci 0 07 0 22 a trial of acetylcysteine n 83 showed that it was highly effective in preventing contrast nephropathy 90 relative risk reduction 110 there have been many more trials and many meta analyses on this topic the latest meta analysis 136 shows a non statistically significant 27 relative risk reduction with acetylcysteine a trial of 129 stunted jamaican children found that both nutritional supplementation and psychosocial stimulation improved the mental development of stunted children children who got both interventions had additive benefits and achieved scores close to those of nonstunted children 117 with long term follow up however it was found that the benefits were small and the 2 interventions no longer had additive effects 137 it is possible that high profile journals may tend to publish occasionally very striking findings and that this may lead to some difficulty in replicating some of these findings 163 poynard et al truth survival in clinical research an evidence based requiem evaluated the conclusions of hepatology related articles published between 1945 81ya and 1999 27ya and found that overall 60 of these conclusions were considered to be true in 2000 26ya and that there was no difference between randomized and nonrandomized studies or high vs low quality studies allowing for somewhat different definitions the higher rates of refutation and the generally worse performance of nonrandomized studies in the present analysis may stem from the fact that i focused on a selected sample of the most noticed and influential clinical research for such highly cited studies the turnaround of truth may be faster in particular non randomized studies may be more likely to be probed and challenged than non randomized studies published in the general literature comparison of evidence on harms of medical interventions in randomized and nonrandomized studies papanikolaou et al 2006 20ya background information on major harms of medical interventions comes primarily from epidemiologic studies performed after licensing and marketing comparison with data from large scale randomized trials is occasionally feasible we compared evidence from randomized trials with that from epidemiologic studies to determine whether they give different estimates of risk for important harms of medical interventions method we targeted well defined specific harms of various medical interventions for which data were already available from large scale randomized trials 4000 subjects nonrandomized studies involving at least 4000 subjects addressing these same harms were retrieved through a search of medline we compared the relative risks and absolute risk differences for specific harms in the randomized and nonrandomized studies results eligible nonrandomized studies were found for 15 harms for which data were available from randomized trials addressing the same harms comparisons of relative risks between the study types were feasible for 13 of the 15 topics and of absolute risk differences for 8 topics the estimated increase in relative risk differed more than 2 fold between the randomized and nonrandomized studies for 7 54 of the 13 topics the estimated increase in absolute risk differed more than 2 fold for 5 62 of the 8 topics there was no clear predilection for randomized or nonrandomized studies to estimate greater relative risks but usually 75 6 8 the randomized trials estimated larger absolute excess risks of harm than the nonrandomized studies did interpretation nonrandomized studies are often conservative in estimating absolute risks of harms it would be useful to compare and scrutinize the evidence on harms obtained from both randomized and nonrandomized studies in total data from nonrandomized studies could be juxtaposed against data from randomized trials for 15 of the 66 harms table 1 all of the studied harms were serious and clinically relevant the interventions included drugs vitamins vaccines and surgical procedures a large variety of prospective and retrospective approaches were used in the nonrandomized studies including both controlled and uncontrolled designs table 1 for 5 38 of the 13 topics for which estimated increases in relative risk could be compared the increase was greater in the nonrandomized studies than in the respective randomized trials for the other 8 topics 62 the increase was greater in the randomized trials the estimated increase in relative risk differed more than 2 fold between the randomized and nonrandomized studies for 7 54 of the 13 topics symptomatic intracranial bleed with oral anticoagulant therapy topic 5 major extracranial bleed with anticoagulant v antiplatelet therapy topic 6 symptomatic intracranial bleed with asa topic 8 vascular or visceral injury with laparoscopic v open surgical repair of inguinal hernia topic 10 major bleed with platelet glycoprotein iib iiia blocker therapy for percutaneous coronary intervention topic 14 multiple gestation with folate supplementation topic 13 and acute myocardial infarction with rofecoxib v naproxen therapy topic 15 differences in relative risk beyond chance between the randomized and nonrandomized studies occurred for 2 of the 13 topics the relative risks for symptomatic intracranial bleed with oral anticoagulant therapy topic 5 and for vascular or visceral injury with laparoscopic versus open surgical repair of inguinal hernia topic 10 were significantly greater in the nonrandomized studies than in the randomized trials between study heterogeneity was more common in the syntheses of data from the nonrandomized studies than in the syntheses of data from the randomized trials there was significant between study heterogeneity p 0 10 on the q statistic among the randomized trials for 2 data syntheses topics 3 and 14 and among the nonrandomized studies for 5 data syntheses topics 4 7 8 13 and 15 the adjusted and unadjusted estimates of relative risk in the nonrandomized studies were similar see online appendix 4 available at www cmaj ca cgi content full cmaj 050873 dc1 the randomized trials usually estimated larger absolute risks of harms than the nonrandomized studies did for 1 topic the difference was almost 40 fold young karr 2011 15ya deming data and observational studies a process out of control and needing fixing as long ago as 1988 1 2 it was noted that there were contradicted results for case control studies in 56 different topic areas of which cancer and things that cause it or cure it were by far the most frequent an average of 2 4 studies supported each association and an average of 2 3 studies did not support it for example 3 studies supported an association between the anti depressant drug reserpine and breast cancer and 8 did not it was asserted 2 that much of the disagreement may occur because a set of rigorous scientific principles has not yet been accepted to guide the design or interpretation of case control research mayes et al 1988 38ya a collection of 56 topics with contradictory results in case control research feinstein 1988 38ya scientific standards in epidemiologic studies of the menace of daily life we ourselves carried out an informal but comprehensive accounting of 12 randomized clinical trials that tested observational claims see table 1 the 12 clinical trials tested 52 observational claims they all confirmed no claims in the direction of the observational claims we repeat that figure 0 out of 52 to put it another way 100 of the observational claims failed to replicate in fact 5 claims 9 6 are statistically significant in the clinical trials in the opposite direction to the observational claim to us a false discovery rate of over 80 is potent evidence that the observational study process is not in control the problem which has been recognised at least since 1988 38ya is systemic the females eating cereal leads to more boy babies claim translated the cartoon example into real life the claim appeared in the proceedings of the royal society series b it makes essentially no biological sense as for humans the y chromosome controls gender and comes from the male parent the data set consisted of the gender of children of 740 mothers along with the results of a food questionnaire not of breakfast cereal alone but of 133 different food items compared to only 20 colors of jelly beans breakfast cereal during the second time period at issue was one of the few foods of the 133 to give a positive we reanalysed the data 6 with 262 t tests and concluded that the result was easily explained as pure chance young et al 2009 17ya cereal induced gender selection most likely a multiple testing false positive the us center for disease control assayed the urine of around 1000 people for 275 chemicals one of which was bisphenol a bpa one resulting claim was that bpa is associated with cardiovascular diagnoses diabetes and abnor...