Medical School MD + DO Mastery

A 4-year, board-aligned study system for medical school and licensing exams.

Walk the full Year 1–4 curriculum — foundational sciences, organ-system blocks, clinical clerkships and advanced practice — each with mastery checklists and linked learning resources, plus a dedicated review system for school exams, Shelf/COMAT, USMLE Step 1–3 and COMLEX-USA Levels 1–3.

BIOSTATISTICS, EPIDEMIOLOGY + EBM

YEAR 1 | PAGE 44C - STUDY DESIGN, DIAGNOSTIC TESTS, EFFECTS + TRIAL INTERPRETATION

BIOSTATS FRAME: DESIGN -> DIRECTION OF SAMPLING -> MEASURE / DENOMINATOR -> BIAS / CONFOUNDING -> ESTIMATE + PRECISION -> CLINICAL INTERPRETATION. REBUILD THE 2x2 TABLE WHEN THE STEM TURNS QUANTITATIVE. H. BIOSTATS / EPI / EBM REVIEW MAP

DomainMust retrieve without notesApplication
Study designRCT, cohort, case-control, cross-sectional, ecological, diagnostic, systematic review/meta-analysis.Identify how subjects were selected and what measure can validly be estimated.
Disease / effect measures Diagnostic testsIncidence, prevalence, RR, OR, ARR/ARI, RRR, NNT/NNH, hazard concepts. Sensitivity/specificity, PPV/NPV, likelihood ratios, cutoff shifts and prevalence effects.Choose correct denominator and interpret effect in plain language. Reconstruct 2x2 table and distinguish test characteristics from post-test predictive value.
InferenceMean/median, SD/SEM, CI, p value, Type I/II error, power, effect size and precision.Separate statistical significance from precision, magnitude and clinical significance.
Validity / EBMSelection/information/recall/observer bias; confounding; effect modification; randomization/blinding; attrition; PICO.Read a trial/abstract for design quality, endpoint, effect, precision and applicability.

BIOSTATS FRAME: DESIGN -> DIRECTION OF SAMPLING -> MEASURE / DENOMINATOR -> BIAS / CONFOUNDING -> ESTIMATE + PRECISION -> CLINICAL INTERPRETATION. REBUILD THE 2x2 TABLE WHEN THE STEM TURNS QUANTITATIVE. H. BIOSTATS / EPI / EBM REVIEW MAP — I. DEEP REVIEW RESOURCES - DIRECT & PLAYABLE

Study Designs - Osmosis - RCT, cohort, case-control, cross-sectional and ecological designs. How to Solve USMLE Step 1 Biostatistics - Randy Neil, MD - 2x2 tables, designs and quantitative strategy. Biostatistics Questions Fast - Randy Neil, MD - board-style rapid calculation and interpretation. Case-Control vs Cohort - Randy Neil, MD - sampling direction -> OR vs RR. Sensitivity, Specificity, PPV, NPV - Dirty Medicine - diagnostic-test discrimination and prevalence effects. How to Appraise a Clinical Trial - Strong Medicine - validity, endpoints, effect size and clinical interpretation.

BIOSTATS FRAME: DESIGN -> DIRECTION OF SAMPLING -> MEASURE / DENOMINATOR -> BIAS / CONFOUNDING -> ESTIMATE + PRECISION -> CLINICAL INTERPRETATION. REBUILD THE 2x2 TABLE WHEN THE STEM TURNS QUANTITATIVE. H. BIOSTATS / EPI / EBM REVIEW MAP — J. TOP 10 MOST-MISSED CONCEPTS - #7 TO #8 7. Identify the study design before selecting the formula Deep explanation

The way participants are sampled determines what can be estimated. Cohorts start with exposure and follow toward outcome; case-control studies start with outcome and look backward toward exposure. The design sets the valid association measure.

BIOSTATS FRAME: DESIGN -> DIRECTION OF SAMPLING -> MEASURE / DENOMINATOR -> BIAS / CONFOUNDING -> ESTIMATE + PRECISION -> CLINICAL INTERPRETATION. REBUILD THE 2x2 TABLE WHEN THE STEM TURNS QUANTITATIVE. H. BIOSTATS / EPI / EBM REVIEW MAP — J. TOP 10 MOST-MISSED CONCEPTS - #7 TO #8 7. Identify the study design before selecting the formula Deep explanation

ResourceDescriptionLink
Why learners miss itFormula memorization encourages learners to search for numbers before understanding the study.

BIOSTATS FRAME: DESIGN -> DIRECTION OF SAMPLING -> MEASURE / DENOMINATOR -> BIAS / CONFOUNDING -> ESTIMATE + PRECISION -> CLINICAL INTERPRETATION. REBUILD THE 2x2 TABLE WHEN THE STEM TURNS QUANTITATIVE. H. BIOSTATS / EPI / EBM REVIEW MAP — J. TOP 10 MOST-MISSED CONCEPTS - #7 TO #8 7. Identify the study design before selecting the formula Deep explanation

Easiest clueAsk: how did subjects enter the study? That usually reveals the design and the correct measure.
8. Sensitivity/specificity are test properties; predictive values depend on the tested population Deep explanationSensitivity and specificity condition on disease status, while PPV/NPV condition on the test result. Changing prevalence shifts PPV and NPV even when sensitivity/specificity stay unchanged.
Why learners miss it Easiest clueAll four metrics are taught in one 2x2 table and the conditioning direction is easily reversed. Read the denominator. Disease column -> sensitivity/specificity; test-result row/column -> predictive value.

K. EBM / CALCULATION ERROR-LOG TAGS

TagTypical missRepair
DESIGN DENOMINATORWrong study type or sampling direction. Correct concept name, wrong population in denominator.Write entry criterion and time direction before formula. Rebuild 2x2 table or write numerator/denominator in words.
VALIDITY INFERENCE 2026/27 foundational-review expanded edition - verify school and official exam updates before testingMissed bias/confounding/attrition/generalizability threat. Treated p, CI, power, effect size and clinical importance as synonyms.State mechanism of distortion and which design feature addresses it. Interpret each statistic in one plain-language sentence.