1. Obtain the value of z to be used to determine 87% confidence interval with

n= 22.

(b) Obtain the value of t to be used to determine 98.0% confidence interval with

n=15.

(c) While determining 95% confidence interval for population mean, will you use z

or t when it is given that a sample of 12 items has mean of 45 and variance 3.8?Obtain the value of z or t you have chosen for this problem.

2. For a given production system a sample of 19 items was taken to obtain 99%

confidence interval for the mean length.The average length of this sample was found to be 20 with a standard deviation of 3.

Determine 99% confidence interval of the population mean length.