The discussion of standard deviation is similar. Damon says he tried the method with some simple numbers and it worked, so he thought it should be true. "OK," says Mr. Hamilton. "So we think it's likely to be true. But how do we know it will be? Are there any hints in anything we have written down?" Damon then suggests that they write out the formula for standard deviation and replace all the values of x with 10.9x. It takes a while to work through the details, but the class ultimately shows that if every number in a data set is multiplied by a constant, the standard deviation of the resulting data set equals the standard deviation of the original data set multiplied by the same constant.