So for example, if this is one standard deviation above, this is one standard deviation below, this point right over here would be eight centimeters more than 178, so that would be 186. And this would be eight centimeters below that, so this would be 170 centimeters. So this is for the random variable m. Now let's think about the random variable w. The random variable w, the mean of w, they tell us, is 170. And one standard deviation above the mean is going to be six centimeters above the mean. The standard deviation is six, six centimeters. So this would be minus six, is to go to one standard deviation below the mean. Now let's think about the difference between the two, the random variable d. So let me think about this a little bit.