6.14
Suppose the standard deviation for Problem 6.8 is unknown but the mean is still 22 feet. If 72.4% of all U.S. Class A warehouses have a clear height less than 20 feet?
P(x > 18.5 | µ = 22 and = ?)
% = 72.4 – 50.0 = 22.4% = 0.224 = 0.59 (from Table A.5)
7.14
A population is normally distributed, with a mean of 23.45 and a standard deviation of 3.8. What is the probability of each of the following?
a) Taking a sample of size 10 and obtaining a sample mean of 22 or more
n = 10
= 22
µ = 23.45
= 3.8
The probability of a z-value of -1.21 is:
0.3869 (from 22 to the mean of 23.45) + 0.5000 = 0.8869 => 88.69%