18
practice examMultiple Choice

Practice Exam

Question 18 • Statistics

The distribution of the number of items washed in a standard load of laundry is skewed left with a mean of 41 items and a standard deviation of 7 point 7 items. What is the probability that 50 randomly selected loads of laundry have a mean of more than 39 point 5 items?

Answer
A
0 point 4 2 2 8
B
0 point 9 1 6 2
C
0 point 8 6 1 9
D
0 point 0 8 3 8

Explanation

For 50 loads, the sampling distribution of the mean is approximately normal, with mean 41 and standard error 7.7/√50 ≈ 1.09. The z-score for 39.5 items is (39.5 − 41)/1.09 ≈ −1.38. Thus, the probability of a sample mean greater than 39.5 is about 0.9162, so the correct choice is 0.9162.

AI-written and checked against the verified answer.

Previous
Next