The time to repair an electronic device is a normally distri

The time to repair an electronic device is a normally distributed random variable measured in hours. It is believed that the true average time to repair such a device is 225 hours. Which of the following 95% confidence intervals would lead to rejecting the claim that the average time to repair the devices is 225 hours?

Solution

The CI in which 225 does not lie within the two limits is the one where we reject this claim. CI contains the plausible values of mean, and we reject null if test mean is not within limits of CI