Descriptive, Diagnostic, Incidence and Survival Statistics
Data types, summary and graphical measures, two-by-two tables, diagnostic accuracy, prevalence, incidence, likelihood ratios, ROC and survival.
How to prepare for MRCPsych Paper B
Integrate clinical formulation, safety and current UK practice with disciplined appraisal of design, bias, estimates and applicability.
Core concepts
Concept 1
Data type and distribution guide summaries: means and standard deviations suit many symmetric continuous data, while medians and interquartile ranges resist skew and outliers.
Exam cue: Write the two-by-two table and label disease status and test result before calculating accuracy measures.
Concept 2
Diagnostic and survival measures depend on explicit denominators, time and setting; likelihood ratios update odds, while predictive values change with prevalence.
Exam cue: Distinguish risk over a period, incidence rate per person-time and time-to-event probability.
Risk pitfalls and guardrails
Treating sensitivity or specificity as the probability that an individual result is correct.
Guardrail: Do not choose an option because it is merely familiar or associated; show why it best answers this lead-in.
Comparing survival proportions without accounting for censoring and differing follow-up.
Guardrail: Do not choose an option because it is merely familiar or associated; show why it best answers this lead-in.
Memory anchors
What is sensitivity?
The proportion of people with the target condition who test positive.
What is specificity?
The proportion of people without the target condition who test negative.
Why do predictive values change across settings?
They depend on the prevalence or pre-test probability as well as test performance.
What does a positive likelihood ratio express?
How much more likely a positive result is in someone with the condition than in someone without it.
What does a Kaplan-Meier curve estimate?
The probability of remaining event-free over time while accounting for censored observations.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A symptom-score distribution is approximately symmetric without extreme values. Which pair best summarises its centre and spread?
Hospital length of stay is strongly right-skewed because a few patients remain for a year. Which summary is most robust?
Answer all questions to submit.
Next step personalized recommendations
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Move forward only after this module is stable.
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