# Essay on Quality Associates

864 Words4 Pages
Hypothesis
Quality Associates, Inc. is a consulting firm that advises its clients about sampling and statistical procedures that can be used to control manufacturing processes. In one case, a client provided Quality Associates with a sample of 800 observations that were taken during a time when the client's process was operating satisfactorily. The sample standard deviation for these data was .21, hence, the population standard deviation was assumed to be .21. Quality Associates then suggested that random samples of size 30 be taken periodically to monitor the process on an ongoing basis. By analyzing the new samples, the client could quickly learn whether the process was operating satisfactorily. When the process was not operating
The sample does not provide enough evidence to support the claim that mean is significantly different from 12
Sample 2
Z Test of Hypothesis for the Mean Data
Null Hypothesis μ= 12
Level of Significance 0.01
Population Standard Deviation 0.21
Sample Size 30
Sample Mean 12.03 Intermediate Calculations
Standard Error of the Mean 0.038340579
Z Test Statistic 0.747684761 Two-Tail Test
Lower Critical Value -2.575829304
Upper Critical Value 2.575829304 p-Value 0.454650325
Do not reject the null hypothesis

Conclusion : Fails to reject the null hypothesis. The sample does not provide enough evidence to support the claim that mean is significantly different from 12 .

Sample 3
Z Test of Hypothesis for the Mean Data
Null Hypothesis μ= 12
Level of Significance 0.01
Population Standard Deviation 0.21
Sample Size 30
Sample Mean 11.89 Intermediate Calculations
Standard Error of the Mean 0.038340579
Z Test Statistic -2.895104947 Two-Tail Test
Lower Critical Value -2.575829304
Upper Critical Value 2.575829304 p-Value 0.003790318
Reject the null hypothesis

Conclusion : Reject the null hypothesis. The sample provide enough evidence to support the claim that mean is significantly different from 12 .
Sample 4
Z Test of Hypothesis for the Mean Data
Null Hypothesis μ= 12
Level of Significance 0.01
Population Standard Deviation 0.21
Sample Size 30