I submitted this question the other week to my tutor, but it was wrong. the only thing correct was the mean. He did not tell me why it was wrong or the correct answers.
Can anybody tell me why this is wrong please? And where I went wrong?
Question and my answer below:
On
Using the formulas from This Question, I noticed that the formulas are different from what you are using, specially in the denominator of the Variance.
I obtained the following values:
I think that your method is correct. However, one place you might have messed up is rounding $\bar{x}=22.3981$ to $22.39$, when it is actually closer to $22.40$, as this might've messed up your answer. You should keep the value as $22.3981$ during calculations.