Question 1

What is standard deviation?

Accepted Answer

Standard deviation measures how spread out a set of numbers is from the mean. A low standard deviation means the numbers are close to the average; a high standard deviation means they are spread out over a wider range.

Question 2

What is the difference between population and sample standard deviation?

Accepted Answer

Population standard deviation (σ) divides the squared deviations by N (total count) and is used when your data represents the entire population. Sample standard deviation (s) divides by N − 1 (Bessel's correction) and is used when your data is a sample of a larger population.

Question 3

What is variance?

Accepted Answer

Variance is the square of the standard deviation. It represents the average of the squared differences from the mean.

Question 4

How is standard deviation calculated?

Accepted Answer

1) Calculate the mean. 2) Subtract the mean from each number and square the result. 3) Find the average of those squared differences (this is the variance). 4) Take the square root of the variance to get the standard deviation.

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