CPH (Other exams) cheat sheet

Incidence rate = new cases / person-time at risk; cumulative incidence = new cases / persons at risk at start.

Prevalence = incidence × average duration of disease (steady-state assumption).

Attack rate = new cases among exposed or in outbreak cohort / total at risk, expressed as a percentage.

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV depends on prevalence, sensitivity, and specificity.

Crude mortality rate = deaths / mid-year population × 100,000; adjust for age when comparing populations.

Relative risk = risk in exposed / risk in unexposed; attributable risk = risk in exposed − risk in unexposed.

Odds ratio approximates relative risk only when the outcome is rare (typically <10%).

Herd immunity threshold = 1 − 1/R0; higher R0 requires higher vaccination coverage.

Screening test validity is assessed with sensitivity and specificity; reliability is assessed with kappa or intraclass correlation.

Core public health functions: assessment, policy development, and assurance.

Ten Essential Public Health Services map onto the three core functions and guide program design.

Levels of prevention: primary (prevent onset), secondary (early detection), tertiary (limit disability).

Policy analysis compares alternatives on effectiveness, efficiency, equity, and feasibility.

Cost-effectiveness ratio = net cost / health outcome gained (e.g., cost per QALY).

Outbreak investigation steps: verify diagnosis, confirm outbreak, define cases, generate hypotheses, control, communicate.

Risk communication principles: transparency, timeliness, consistency, and acknowledgment of uncertainty.

Health in All Policies requires intersectoral collaboration across transportation, housing, education, and environment.