Exercise 7.11.3

Model Answers to 07 Hypothesis Testing in Six Sigma Statistics using Minitab 17, Green Belt Edition.

Example 7.11.3

Conduct a 1 sample t Test


Analyse the data in File 07Hypothesis Testing.xlsx worksheet Ex 7.11.3 and answer the questions shown below. The data was collected randomly and is recorded in time order.

  1. Is the sample data within Column Pressure likely to have come from a population where the mean was different to 77?
  2. What is the confidence interval for the mean of the population?
  3. Have the requirements of the test that you have used been met?
  4. What was the Power of the test when you want to detect a difference of 2?
  5. Are there any issues associated with this level of  Power ?
  6. Does the Report Card generate any warnings?



Set-Up

Analysis

1.  Click Stat <<Assistant<< Hypothesis Tests

2. Click on 1 Sample t



2.  Complete the menu as shown and click OK to execute the procedure.


Starting from the top left of the Summary Report, the sample data within Column Pressure is likely to have come from a population where the mean was different to 77.



The confidence interval for the mean of the population was 73.85 to 76.45, which is obviously lower than the target we were checking against.

Also, note that the sample size was 75 which shows that we met the minimum sample size requirement for normality not to be an issue.


On the Diagnostic Report we see that the control chart shows that there were no usual data points that could affect the validity of the test.

It also shows the distribution was not bi-modal.



 On the Power Report we see that a Power of 85.6% was achieved. There are no issues with this level of Power as a difference was detected.



The Report Card did not show any warnings.