SOLUTION: Life tests performed on a sample of 13 batteries of a new model indicated: (1) an average life of 75 months, and (2) a standard deviation of 5 months. Other battery models, produce

Question 1149100: Life tests performed on a sample of 13 batteries of a new model indicated: (1) an average life of 75 months, and (2) a standard deviation of 5 months. Other battery models, produced by similar processes, have normally distributed life spans. The 98% confidence interval for the population mean life of the new model is _________.
A)61.60 to 88.41
B)63.37 to 86.63
C)71.77 to 78.23
D)79.86 to 81.28
E)71.28 to 78.72

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
half-interval i z*sigma/sqrt(n),or 2.328*5/sqrt(13)
This product is 3.23
the interval would be 75+/- 3.23
this is(71.77, 78.23)
C
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