Which measure of central tendency is most appropriate for summarising serial dilution antibody titres such as 1:4, 1:8, 1:16 and 1:32 obtained after vaccination?

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

Explanation

Antibody titres follow a logarithmic progression because each dilution step doubles the previous value, producing a log-normal distribution. The geometric mean, the antilog of the mean of the logarithms of the values, gives the true average titre, whereas the arithmetic mean is pulled upward toward the highest titre and overstates the group response. The median discards information from all values except the middle one.

Reference: Mahajan's Methods in Biostatistics for Medical Students and Research Workers, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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