A sample of 20 small bags of the same brand of candies was s

A sample of   20   small bags of the same brand of candies was selected. Assume that the population distribution of bag weights is normal. The weight of each bag was then recorded. The mean weight was   5   ounces with a sample standard deviation   s=0.3   ounces. We would like to calculate an 80% confidence interval for the average weight of a sample of size   20 .

sx= _______

The critical   t   value for an 80% confidence interval is

tcrit= ________

EBM=sxtcrit= _____

An   80%   confidence interval for the population average weight of the candies is from______

   to _______

Solution

Sx = 0.3 / srqt (60) = 0.0387

for alpha = 1 - 0.80 = 0.20

alpha/2 = 0.10

df = 20-1=19

critical value of T = +/- 1.328

EBM = 0.0387*1.328 = 0.051

interval : 5 +/- 0.051

4.949 < miu < 5.051