Answer:
The standard deviation is 1.5 inches.
Step-by-step explanation:
For a normal curve, we have that the area between the mean and the mean plus two times the standard deviation is something around 47.5%
Then the area between the mean minus two times the standard deviation and the mean plus two times the standard deviation is equal to the 95%.
the mean is 66
if the standard deviation is x, we have that:
66 + 2*x = 69
66 - 2*x = 63
then we can find that:
2*x = 66 - 63 = 3
x = 3/2 = 1.5
The standard deviation is 1.5 inches.
