Antibody titres against a viral vaccine are reported as 1:2, 1:4, 1:8, 1:16 and 1:32 in five subjects. Which measure of central tendency is most appropriate for summarising this data?
- A Arithmetic mean
- B Median
- C Geometric mean ✓
- D Mode
Correct answer: C. Geometric mean
Explanation
Titres form a logarithmic progression where each value is a multiple of the previous one, producing a log-normal distribution. The geometric mean, calculated as the antilog of the mean of the logs of the values, best represents such multiplicative data and is the conventional summary measure for antibody titres. The arithmetic mean is pulled upward by the highest titre and overestimates the central value. Median is acceptable but not the conventional choice for serial dilution data.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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