Behavioral & Public Health confusion pairs
24 Behavioral & Public Health topics students commonly mix up on Step 1, each with the fastest separator, a side-by-side comparison, and a free practice question.
- Sensitivity vs SpecificitySensitivity: true positive rate, rules disease out when negative (SnNout); specificity: true negative rate, rules disease in when positive…Video
- Positive predictive value vs Negative predictive valuePPV asks disease given positive; NPV asks no disease given negative, and both shift with prevalence.Video
- Type I error vs Type II errorType I error (alpha): false positive, rejecting a true null; type II error (beta): false negative, missing a real effect.Video
- Number needed to treat vs Number needed to harmNNT: patients treated to prevent one bad outcome (1 / ARR), lower is better; NNH: patients treated to cause one harm (1 / ARI), higher is…
- Relative risk vs Odds ratio and hazard ratioRR: risk ratio for cohorts and trials; OR: odds ratio for case-control; HR: hazard ratio for time-to-event survival analysis.
- Incidence vs PrevalenceIncidence is new cases over time; prevalence is all existing cases and roughly equals incidence multiplied by disease duration when…Video
- Cohort study vs Case-control studyCohort: starts from exposure and follows forward for outcomes (incidence, RR); case-control: starts from outcome and looks back at…
- Randomized controlled trial vs Observational cohort and cross-sectional studiesRCT assigns exposure; cohort observes exposure over time; cross-sectional snapshots one time point.
- Crossover trial vs Parallel trialCrossover trial: each patient receives both treatments in sequence as their own control; parallel trial: each patient stays in one group.
- Selection and recall bias vs Lead-time, length-time, and confounding biasSelection/recall distort who enters or remembers; lead/length distort screening survival; confounding is a lurking third variable.
- Validity vs ReliabilityValidity asks whether the tool measures the intended truth correctly; reliability asks whether repeated measurements are consistent and…
- Accuracy vs PrecisionAccuracy: closeness to the true value (low systematic error); precision: closeness of repeated measures to each other (low random error).
- Confidence interval vs P-valueCI estimates effect range and precision; p-value quantifies incompatibility with the null under assumptions.
- Median in skewed distributions vs Mean and modeMedian resists skew and outliers; the mean is pulled toward the tail and the mode is simply the most frequent value.
- Normal distribution vs Skewed distributionNormal is symmetric with aligned center measures; skewed is asymmetric with mean pulled toward tail.
- Predictive values affected by prevalence vs Intrinsic test characteristicsPrevalence changes post-test probability, so PPV rises and NPV falls as prevalence increases; sensitivity and specificity stay intrinsic…
- Beneficence and nonmaleficence vs Autonomy and justiceBeneficence helps, nonmaleficence avoids harm, autonomy respects choice, justice is fairness.
- Informed consent vs Implied consent and assentInformed consent is explicit informed authorization; implied consent is emergency/routine context; assent is child agreement.
- Capacity vs CompetenceCapacity: a clinical, decision-specific judgment made by a physician; competence: a global legal status determined by a court.
- Living will vs Durable power of attorneyLiving will: written instructions for the care you want; durable power of attorney: names a person to decide for you.
- Confidentiality vs Mandatory reporting and public health exceptionsConfidentiality is default privacy; mandatory reporting overrides it for safety and public health duties.
- Active euthanasia vs Passive euthanasiaActive euthanasia directly causes death; passive withholding/withdrawing allows underlying disease to proceed.
- Withholding care vs Withdrawing careWithholding is not starting; withdrawing is stopping, and ethically they are treated similarly when aligned with patient goals.
- Routine medical confidentiality vs Duty to warn/protect and reportable exceptionsRoutine confidentiality is the default; identifiable danger or mandated reporting creates the exception.