Testing Goodness-of-Fit with a Normal Distribution An observed frequency distribu- tion of sample IQ scores is as follows:
|
IQ score
|
Less than
80
|
80-95
|
96-110
|
111-120
|
More than
120
|
|
Frequency
|
20
|
20
|
80
|
40
|
40
|
a. Assuming a normal distribution with m 5 100 and s 5 15, find the probability of a randomly selected subject belonging to each class. (Use class boundaries of 79.5, 95.5, 110.5, and 120.5.)
b. Using the probabilities found in part (a), find the expected frequency for each category.
c. Use a 0.01 significance level to test the claim that the IQ scores were randomly selected from a normally distributed population with m 5 100 and s 5 15.