Question

In a population of chickens, the average (arithmetic mean) weight is 6.3 pounds, and the standard deviation is 1.2 pounds. Which of the following weights (in pounds) are within 1.5 units of standard deviation of the mean?

Indicate all weights.

A. 4.4
B. 4.6
C. 5.1
D. 5.2
E. 6.9
F. 7.6
G. 7.7
H. 8.2

Answer 1

why is it 1.8 instead of 1.7 ??? Why don't you add 0.5 to 1.2??? Why do you multiply 1.5 to 1.2?

Answer 2

1.5 means one and a half, so one and a half of 1.2 is 1.2*(1.5) or 1.2+0.6=1.8.
The mean is 6.3 lb. So withing (plus or minus) 1.5 standard deviations is 6.3\(\pm\) 1.8, or all weights between 4.5 and 8.1lbs.