A serological survey reports antibody titres against dengue as 1:10, 1:20, 1:40, 1:80 and 1:160 in five subjects. Which measure of central tendency is most appropriate to summarise these values?

• A Arithmetic mean
• B Median
• C Harmonic mean
• D Geometric mean ✓

Explanation

Antibody titres are serial dilutions that increase logarithmically, so they should be averaged after log transformation. The geometric mean is the antilog of the mean of the logs and gives the correct average titre. The arithmetic mean would be unduly inflated by the highest titre because the data are exponentially spaced, and it does not correspond to any real dilution step on the twofold series used in serology.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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