The SD is the r.m.s. of the deviations. Work carefully through the example on page 67 to understand the calculation. The SD is measured in the same units as the data. It measures how much the data is spread out. We see the second list is twice as spread out as the, which agrees with our intuition.
Most calculators have two buttons for computing the standard deviation of a list.
If your calculator has a button marked s , check it using an example in the book to make sure that your calculator is using the same formula. Once you can use the right function on your calculator, you can avoid doing these calculations by hand. If you have a spreadsheet on your computer, you may be able to use it to compute the SD and to sort lists. Check your program. The normal curve, pictured on page 74, is the most frequenty used curve in statistics.