First find the mean (sum divided by number of values) 4+5+8+10+15=42 42/5=8.4 Then find the difference between each of the numbers and the mean. 4.4, 3.4, 0.4, 1.6, 6.6 Then find the mean of those values. 4.4+3.4+0.4+1.6+6.6=16.4 16.4/5=3.28 Final answer: 3.28