The population of lengths of aluminum-coated steel sheets is normally distributed with a mean of 30.05 inches and a standard deviation of 0.3 inches.What is the probability that average length of a steel sheet from a sample of 9 units is more than 29.95 inches long?
A)4602
B)8413
C)1587
D)5397

Question

Quizplus · Accepted Answer

The standard error of the mean is 0.3/sqrt(9) = 0.1. The z-score for 29.95 is (29.95-30.05)/0.1 = -1. The probability of a z-score being greater than -1 is 0.8413.

The Population of Lengths of Aluminum-Coated Steel Sheets Is Normally