Longbrite candles are supposed to burn for at least 7 hours. To check, a random sample of 30 are tested. The time (t) before they burn out is recorded. The results are:
Carry out a test at the 10% significance level of whether the Longbrite candles, on average, burn for at least 7 hours.
So I've stated the two hypotheses, equal to and less than 7. I've calculated that the mean of the sample:
But when I try to calculate the unbiased sample variance, I get:
Would anyone be able to point out where I'm going wrong with that variance? The textbook solutions say that S=0.3084, but I'm not quite sure why! Thank you!