explain, what are they trying to find here- deviation s. Remember that s has n 2 1 as a denominator rather than N. Again, let's use the Yukon police arrests example to illustrate the estimating accuracy of the sample standard deviation. The population standard deviation is 3.7. (If you do not believe us, calculate it from the data in Table 10.2.) Drawing a sample of five officers, we get the estimate of the standard deviation shown in Table 10.4 (note that we use the same sample in this illustration that we used before). Our estimate of the population standard deviation is 3.85, which is close to the population value of 3.7. Note that had we divided by n rather than by n 2 1, the standard deviation estimate would have been 3.4. Dividing by n gives us a consistently low estimate of the population standard deviation. For this reason, the estimate always is made with a denominator of n 2 1. Most statistical programs calculate the sample standard deviation, not the population standard deviation. When you use a statistical package, you need to be aware of this fact