Question 1

What is the difference between population and sample standard deviation?

Accepted Answer

Population standard deviation divides by N (total count) and is used when you have data for the entire population. Sample standard deviation divides by N-1 (Bessel's correction) and is used when your data represents a sample from a larger population, providing an unbiased estimate.

Question 2

How do you interpret standard deviation?

Accepted Answer

Standard deviation measures how spread out data is from the mean. A low standard deviation means data points are close to the mean, while a high standard deviation indicates data is spread over a wider range. In a normal distribution, about 68% of data falls within 1 SD, 95% within 2 SD, and 99.7% within 3 SD of the mean.

Question 3

What is the coefficient of variation and when should I use it?

Accepted Answer

The coefficient of variation (CV) is the ratio of standard deviation to the mean, expressed as a percentage. It's useful for comparing variability between datasets with different units or means. A CV below 15% typically indicates low variability, while above 30% suggests high variability.

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