Use the Normal to model the distribution of sample means.
-In a metal fabrication process, metal rods are produced that have an average length of 20.5 feet with a standard deviation of 2.3 feet. A quality control specialist collects a
Random sample of 30 rods and measures their lengths. What is the probability of
Observing a sample mean greater than 21 feet?
A) 0.3830
B) 0.8830
C) 0.4778
D) 0.5222
E) 0.1170

Question

Quizplus · Accepted Answer

The sample mean follows a normal distribution with mean 20.5 and standard deviation 2.3/sqrt(30). The z-score for 21 is (21-20.5)/(2.3/sqrt(30)) = 1.196. The probability of observing a sample mean greater than 21 is 1 - P(Z < 1.196) = 0.1170.

Use the Normal to Model the Distribution of Sample Means