Question 1191081
I would use a t-distribution because the sd used is from the sample. Some might use a z- because the number is large. There won't be a big difference but t is more accurate
half-interval is t(0.995,df=120)*ss/sqrt(n)=2.617*13.3/11
=3.164 min
the interval is (34.036, 40.364)units min.
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95% for first part
5% for second part