Antibody titres against a vaccine are recorded as reciprocals such as 20, 40, 80, 160, 320. The distribution is markedly right-skewed. Which average is most appropriate to summarise these titres?
- A Geometric mean ✓
- B Arithmetic mean
- C Mode
- D Median of raw values
Correct answer: A. Geometric mean
Explanation
Titres form a log-normal series where values progress by doubling, so the geometric mean, the antilog of the mean of log-transformed values, best represents the central value. Indian textbooks conventionally teach the geometric mean for serological titres. The arithmetic mean is inflated by high titres in a right-skewed series. The median is defensible descriptively, but examination convention and standard practice for titre data specify the geometric mean as the answer.
Reference: Mahajan's Methods in Biostatistics for Medical Students, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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