An incubation period is a time between when you contract a virus and when your symptoms start. By surveying randomly selected local hospitals, a researcher was able to obtain the following sample of incubation periods of 19 patients:
6 7 12 8 9
10 9 8 12 8
11 10 11 15 15
9 11 11 7
(Note: The average and the standard deviation of the data are respectively 9.95 day(s) and 2.48 day(s).)
At 1% significance level, test the claim that the average incubation period of the novel coronavirus is greater than 6 day(s). You may also assume that the sample is from a normal population.