You take a sample of 30 seniors and ask them to rate their satisfaction with their chosen major on a scale of 0 to 10 (where 10 represents the highest level of satisfaction). Assume a population standard deviation of 4.0 points. The mean score obtained from your sample was 7.1 points.

Construct a 95% confidence interval around your estimate of the average level of satisfaction with their major.

What assumption did you have to make about the sample in order to generate this confidence intervals?