Evidence and research methods
How Preprints Are Screened Before Posting
Preprint screening checks scope, ethics signals, privacy, duplication, and possible harm, but it does not certify the research through peer review.
Health & Evidence Library
Evidence and research methods
Tools for reading studies, interpreting tests and effect estimates, recognizing uncertainty, and asking whether evidence applies.
207 guides · Page 1 of 4
Evidence and research methods
Research Embargoes and the Ingelfinger Rule
Journal embargoes coordinate reporting around publication; prior-publication rules decide whether earlier sharing affects manuscript eligibility.
Evidence and research methods
Why Context Matters in Screening
A screening test's value depends on population risk, test thresholds, treatment benefit, follow-up capacity, harms, and the full care pathway.
Evidence and research methods
When Not to Pool a Meta-Analysis
A pooled estimate can mislead when studies answer different questions, use incompatible outcomes, contain major bias, or vary in effect direction.
Evidence and research methods
What the STAR*D Reanalysis Debate Teaches About Trial Fidelity
The STAR*D debate shows how outcome definitions, analysis populations, missing data, and protocol fidelity can materially change a trial's headline.
Evidence and research methods
What Real-World Data Sources Actually Look Like
A practical guide to claims, electronic records, registries, devices, and linked data, including what each source records and systematically misses.
Evidence and research methods
What Procalcitonin and CRP Can and Cannot Decide About Antibiotics
How procalcitonin and C-reactive protein can support antibiotic stewardship without replacing diagnosis, severity assessment, cultures, or reassessment.
Evidence and research methods
What Makes Science Communication Trustworthy
Trustworthy science communication makes evidence traceable, calibrates certainty, quantifies effects, discloses interests, and corrects errors visibly.
Evidence and research methods
What Makes a Biomarker Clinically Useful
A useful biomarker must be measurable, valid for a defined purpose, and capable of improving a decision. Association alone is not enough.
Evidence and research methods
What Large Replication Projects Actually Found
Major replication projects found smaller effects, mixed repeatability, and practical barriers. Their results require more nuance than a single failure rate.
Evidence and research methods
What Good Clinical Evidence Looks Like
Good clinical evidence fits a precise question and withstands scrutiny for bias, precision, relevance, transparency, replication, and applicability.
Evidence and research methods
What External Validity Means
External validity asks whether a study's results apply to a defined target beyond the study, across people, settings, treatments, outcomes, and time.
Evidence and research methods
What ctDNA Minimal Residual Disease Can and Cannot Do
Learn how ctDNA molecular residual disease testing estimates recurrence risk, why a negative result cannot prove cure, and when treatment utility needs trials.
Evidence and research methods
Verification Bias in Diagnostic Accuracy Studies
Verification bias occurs when disease confirmation depends on the test result or patient features. Learn how it distorts sensitivity and specificity.
Evidence and research methods
USPSTF Statin Guidance for Primary Prevention
Learn how the USPSTF combines age, risk factors, and 10-year cardiovascular risk when recommending statins to prevent a first heart attack or stroke.
Evidence and research methods
Understanding Standardized Mean Differences
How standardized mean differences combine outcomes measured on different scales, and why scale direction, variability, bias, and context matter.
Evidence and research methods
Understanding Selection Bias in Health Research
Selection bias explained through recruitment, follow-up, referral, missing data, conditioning, and the checks that make study results more credible.
Evidence and research methods
Understanding Competing Risks
Competing events change the meaning of a survival curve. Cumulative incidence, cause-specific hazards, and Fine-Gray models answer different questions.
Evidence and research methods
Umbrella Reviews and Overviews of Reviews
Umbrella reviews synthesize reviews, but overlap, variable methods, stale searches, and inherited bias can overstate certainty.
Evidence and research methods
Trial Registration and Results Reporting
Trial registration records the planned question, while structured results reporting reveals completed studies and outcome changes.
Evidence and research methods
The Table 2 Fallacy: One Model, Many Wrong Questions
A multivariable regression table may display many coefficients, but each causal question can require a different adjustment set and interpretation.
Evidence and research methods
The Placebo Effect, Without the Myths
Placebo responses mix context, natural change, and measurement. Learn what placebo effects can change, what they cannot prove, and why controls matter.
Evidence and research methods
The Nocebo Effect: Symptoms Are Real, Causes Are Mixed
Nocebo effects can amplify symptoms through expectation and learning. Good communication reduces avoidable harm without hiding genuine treatment risks.
Evidence and research methods
Real-World Data After Approval: What It Can Add
After approval, real-world data can detect rare harms and study use in broader populations, but design and data quality determine credibility.
Evidence and research methods
Noninferiority Trials: How the Margin Determines the Claim
Learn how noninferiority margins, assay sensitivity, confidence intervals, missing data, and analysis populations determine whether a trial is credible.
Evidence and research methods
Medical Registries: What They Record and What They Miss
Disease, product, quality, and trial registries serve different purposes. Their credibility depends on coverage, definitions, and follow-up.
Evidence and research methods
Lead-Time Bias: Why Earlier Diagnosis Can Look Like Longer Survival
Earlier diagnosis automatically lengthens measured survival from diagnosis. Learn how mortality trials separate true screening benefit from lead-time bias.
Evidence and research methods
Instrumental Variables: The Assumptions Behind a Natural Experiment
Instrumental-variable studies can address unmeasured confounding only under demanding assumptions. Learn relevance, independence, exclusion, and LATE.
Evidence and research methods
Incidental Findings: How Unexpected Results Should Be Interpreted
Unexpected findings on scans, tests, and sequencing can trigger useful care or harmful cascades. Learn how context and follow-up guidance shape decisions.
Evidence and research methods
Immortal Time Bias: How Misassigned Follow-Up Creates False Benefit
Immortal time bias can make treatment look protective when pre-treatment survival is credited to treatment. Learn how to detect and prevent it.
Evidence and research methods
Hazard Ratios: What They Measure and Why Absolute Risk Still Matters
A hazard ratio compares instantaneous event rates, not simple probabilities. Learn proportional-hazards assumptions, censoring, and better companion measures.
Evidence and research methods
Diagnostic Accuracy Studies: How to Read Sensitivity, Specificity, and Bias
Learn how patient selection, reference standards, thresholds, verification, and prevalence determine whether diagnostic accuracy results will travel.
Evidence and research methods
Contrast in Medical Imaging: What It Adds and How Risk Is Assessed
A practical guide to iodinated, gadolinium-based, ultrasound, and gastrointestinal contrast, including kidney and reaction risk.
Evidence and research methods
Confounding by Indication: Why Treated Groups Start Out Different
Confounding by indication can make helpful treatments look harmful, or ineffective treatments look useful, in observational medical research.
Evidence and research methods
Why Screening Selects Slower Cancers and Inflates Survival Statistics
Length-time bias makes screen-detected cancers look less lethal because screening preferentially finds tumors with longer detectable phases.
Evidence and research methods
Why Retractions Are Rising and What They Mean
Why raw retraction counts are increasing, how paper mills and better detection contribute, and which metrics reveal whether correction works.
Evidence and research methods
Why Retracted Papers Keep Getting Cited
Why retraction notices fail to reach every PDF, reference list, review, guideline, and database, and how to stop unreliable evidence spreading.
Evidence and research methods
Why Research Use Only Is a Red Flag
What Research Use Only means for laboratory products, why it cannot support patient claims, and which evidence a clinical test needs.
Evidence and research methods
Why Pulse Oximeters Miss Low Oxygen in Darker Skin
How pulse oximeters estimate oxygen, why darker pigmentation can bias readings upward, and how safer interpretation reduces missed hypoxemia.
Evidence and research methods
Why Psychotherapy Trials Are Hard to Blind
How awareness of treatment assignment affects psychotherapy trials and which design choices can preserve credible comparisons.
Evidence and research methods
Why Overall Survival Is the Gold Standard in Cancer Trials
Why overall survival is uniquely persuasive in oncology, where it can mislead, and how to read earlier endpoints alongside it.
Evidence and research methods
Why Obesity Drug Trials Differ From Diabetes Drug Trials
How indication, population, endpoints, duration, background care, safety questions, and estimands differ between obesity and diabetes programs.
Evidence and research methods
Why More Medical Testing Is Not Automatically Safer
How low pretest probability, false positives, incidental findings, overdiagnosis, and follow-up harms can make an untargeted test panel unsafe.
Evidence and research methods
Why Global Phase 3 Programs Outgrow One Power Calculation
Why a global confirmatory program may need more participants than the primary efficacy calculation, from safety and regions to subgroups and missing data.
Evidence and research methods
Why FDA Did Not Approve MDMA-Assisted Therapy for PTSD
What FDA's 2024 complete response said about efficacy, safety reporting, functional unblinding, durability, and the path for new evidence.
Evidence and research methods
Why Diabetes Drugs Began Running Cardiovascular Outcomes Trials
How a 2008 FDA safety policy created the modern diabetes CVOT, what those trials test, what they discovered, and how U.S. policy later changed.
Evidence and research methods
Why Cognitive Bias Can Contribute to Diagnostic Error
Bias labels describe recurring reasoning patterns, but diagnostic error also reflects knowledge, data, workload, teamwork, and system design.
Evidence and research methods
Why an AI Tool Cannot Be an Author, and What Researchers Must Disclose
Current medical-publishing rules keep authorship human, require accountable verification, and call for transparent disclosure of AI assistance.
Evidence and research methods
Why Adult Suicide-Risk Screening Received an I Statement
What the USPSTF found insufficient about universal adult suicide-risk screening, and why that does not limit assessment when concern exists.
Evidence and research methods
Who Sees Interim Trial Results, and When Should a Trial Stop?
Data monitoring committees review interim benefit, harm, and futility using prespecified rules while protecting trial integrity.
Evidence and research methods
Who Counts as an Author? ICMJE and CRediT
ICMJE defines who qualifies for authorship; CRediT records contributor roles. Learn how accountability, AI use, groups, and acknowledgments fit.
Evidence and research methods
When Real-World Evidence Helps and When It Misleads
Real-world evidence can describe care, compare outcomes, and detect harms, but confounding, selection, missing data, and timing can mislead.
Evidence and research methods
When One Study Appears in Several Papers
How duplicate publication, fragmented reporting, and legitimate secondary publication affect readers and evidence synthesis.
Evidence and research methods
When a Single Hazard Ratio Hides a Time-Varying Effect
Proportional hazards is an assumption about a stable rate ratio over time. Curves, residuals, and time-based alternatives reveal when it fails.
Evidence and research methods
What statcheck and GRIM Can Reveal From a Paper's Reported Numbers
Automated consistency checks can flag impossible means and mismatched p values, but every flag needs context and human review.
Evidence and research methods
What Blinded Outcome Review Adds to an Open-Label Trial
PROBE trials keep treatment open but blind endpoint assessment. This limits some judgment bias without repairing every consequence of open treatment.
Evidence and research methods
What a Subgroup Analysis Shows
A subgroup analysis tests whether effects differ across groups. Credibility depends on interaction tests, planning, precision, and replication.
Evidence and research methods
What a P Value Really Means
A p value measures how unusual a result is under a stated statistical model. It is not the probability that a hypothesis is true.
Evidence and research methods
What a Normal Lab Reference Range Really Means
A lab reference interval describes results in a defined reference population. It is not a universal border between health and disease.
Evidence and research methods
What a Nonsignificant Result Does and Does Not Show
A practical guide to confidence intervals, power, equivalence tests, and the difference between no evidence of effect and evidence of no effect.