Standard deviation, represented by the Greek Letter sigma σ, is a measure of dispersement in statistics. It shows you how spread out your data set it. In a normal distribution, the bulk (64.2%) of a data set is within one standard deviation from the mean and almost all the data will fall within three standard deviations of the mean.  Calculating a standard deviation by hand involves the use of an ugly-looking formula, but you can calculate a standard deviation in Minitab in a couple of mouse clicks.
Sample question: Find the standard deviation in Minitab for the following data: 102, 104, 105, 110, 112, 116, 124, 124, 125, 240, 245, 254, 258, 259, 265, 265, 278, 289, 298, 311, 321, 321, 324, 354
Step 1: Type your data into a single column in a Minitab worksheet.
Step 2: Click “Stat”, then click “Basic Statistics,” then click “Descriptive Statistics.”

Step 3: Click the variables you want to find the standard deviation for and then click “Select” to move the variable names to the right window.
Step 4: Click the “Statistics” button.
Step 5: Check the “Standard deviation” box and then click “OK” twice. The standard deviation will be displayed in a new window.