A researcher studies correlation between serum vitamin D levels (continuous, non-normally distributed) and muscle strength (continuous, normally distributed). The most appropriate statistical test is:

• A Pearson's product-moment correlation coefficient
• B Kendall's tau
• C Point biserial correlation
• D Spearman's rank correlation coefficient ✓

Explanation

Pearson's correlation requires both variables to be normally distributed (or at least the residuals). When one or both variables are non-normally distributed (as with serum vitamin D which is often right-skewed), Spearman's rank correlation (r_s) is the non-parametric alternative—it uses ranks rather than actual values and is appropriate when normality assumption is violated. Kendall's tau is also non-parametric but less commonly used in medical research and less powerful. Point biserial correlation is for one binary and one continuous variable.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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