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%