construct a 95 CI for the mean Rockwell hardness Construct a

construct a 95% C.I for the mean Rockwell hardness Construct a 95% C.I for the standard deviation of the Rockwell hardness. A sample of 25 households yields a standard deviation of 45.8 gallons per day. Assume normal population and use a = 0.01 to test the hypothesis that the variance of the water usage is less than 2000 gallons per day

Solution

Sample size = 25 = n

s^2 = sample variance = 45.8²

Population variance = 2000

Alpha =0.01

Var sample/var pop = 1.049

chi square = 25.17168

Df = 24

p value = one tailed = 0.1982

p>alpha

Hence accept null hypothesis.

variances are equal and Ha is not true.