The Intelligence Quotient (IQ)test scores are normally distributed with a mean of 100 and a standard deviation of 15.Given a class with 25 students,what is the probability that the class' average IQ score is between 85 and 115?
A)0.4987
B)3.00
C)0.0026
D)0.9974

Question

Quizplus · Accepted Answer

The sampling distribution of the sample mean for 25 students will have the same mean (100) but a smaller standard deviation (15/√25 = 3). Using the standard normal distribution, the probability that the sample mean is between 85 and 115 is approximately 0.9974.

The Intelligence Quotient (IQ)test Scores Are Normally Distributed with a Mean