Answer:
4.140393356
Step-by-step explanation:
Mean = (3+4+5+7+10+12+15) / 7 = 8
Count = 7 numbers
Sum of the numbers = 56
Each number minus the mean =
(3-8=-5)(4-8=-4)(5-8=-3)(7-8=-1)(10-8=2)(12-8=4)(15-8=7)
Now square of each of these numbers:
25+16+9+1+4+16+49 = 120
Variance = 120/7 = 17.14285714
Standard deviation = square root of the variance
Sqrt 17.14285714 = 4.140393356