Question

The Great Eagles of the Misty Mountains wish to estimate the mean number of orcs per raiding party. To do so, they measure the number of orcs in 13 raiding parties. They find an average of 72 orcs per party with a standard deviation of 5.7 orcs in their sample. Compute the 90% confidence interval about the mean number of orcs per raiding party. Answer with the Upper Bound only.

Round to 2 decimal places, as needed.

Answer 1

Solution :

sample size = n = 13

Degrees of freedom = df = n - 1 = 12

t ,df = 1.356

Margin of error = E = t/2,df * (s /n)

= 1.356 * (5.7 / 13)

Margin of error = E = 2.14

The 95% confidence interval estimate of the population mean is,

Upper Bound =   + E

= 72 + 2.14

= 74.14