If the mean of a data set is 50 and the coefficient of variation is 20%, the standard deviation is: MCQ with Answer and Explanation

Explanation:
Geometric mean requires all positive values; otherwise it's undefined or zero. Harmonic mean also requires non-zero values, but GM is more restricted. Actually, GM is defined only for positive data if we want real numbers. So C.

Explanation:
Census is a population count, not a continuous vital event registration. Vital statistics come from civil registration.

Explanation:
The Periodic Labour Force Survey (PLFS) is an official government publication providing comprehensive employment data, making it a reliable source of secondary data for national trends.