Overview: What Is a Pooled Standard Deviation? The definition of the standard deviation is the average distance each data point is away from the mean of the data.

Discover what a log-normal distribution is, its financial applications, and how to calculate it, including using Excel for ...

Key Points Use Excel to calculate daily returns and standard deviation to gauge stock volatility. Annualize volatility by multiplying daily standard deviation by the square root of 252.

The size of the data set—the sample size—doesn't affect standard deviation, but the sample size is a key factor in calculating the SEM.