Help! Please assist with problem below with step-by-step explanation.

While at my job I decided to ask 20 co-workers how often they go to the gym.

I believe the population mean number of the amount of times my co-workers go to the gym is more than 7.

Here are the results:

9 said they go to the gym four days a week.

5said they go to the gym two days a week.

4said they don't go to the gym at all.

2 said they go to the gym three times a week.

Test the hypothesis significance level: = .05