Question

How many of the data set items are within one standard deviation of the mean (in the range chosen on #3)?
*
Data set: 34,45,50,56,60,65,70,70,70,70,72,77,77,80,82,86,86,89,95,98
A. 12
B. 14
C. 16
D. 18

Answer 1

Mean = 1432/20 = 71.6.
Population SD ≈ sqrt(5218.8/20) ≈ 16.16, so one SD range ≈ 71.6 ± 16.16 = [55.44, 87.76].
Values in that range: 56, 60, 65, 70,70,70,70,72,77,77,80,82,86,86 — 14 items.

Answer: B.