Question

QUESTION 7

Suppose that the duration of trouble-free operation of a new vacuum cleaner is normally distributed with a mean of 550 days and a standard deviation of 100 days. The research department randomly selects 25 customers who bought these vacuum cleaners and records the duration (in days) of trouble-free operation. Which of the following is NOT TRUE for the sample average of number of trouble-free operation days (x)?

Question image 1