Standard deviation measures how far numbers in a data set are spread out from an average value. In investing, it is used as a measurement of portfolio volatility.

The larger the sample size, the greater the proportional effect will be on the overall estimate of the standard deviation.

2. Find the daily standard deviation. Now, you will use the STDEV.S function in Excel. Place your cursor in D13 and type '=STDEV.S(D4:D12)' without the quotation marks. This formula calculates the ...