Minitab Notes for Activity 6

Entering the Data (Question 4)

  1. Label an empty column of the worksheet as "mass"
  2. Enter the masses that you collected in question 4 in that column.

Summarize the Sample (Question 6)

  1. Choose Stat / Basic Statistics / Display Descriptive Statistics
  2. Select the mass variable
  3. Click OK.

Finding the Critical Values (Question 13)

The easiest way to find the critical values is to go to Table T in your appendix and look up the value(s).

However, if you want to do this with Minitab, you can do the following. These instructions assume you're using a t distribution. If you're using a normal distribution, then choose normal in step 1 instead of t and ignore the part about degrees of freedom.

  1. Choose Calc / Probability Distributions / t
  2. Check Inverse Cumulative Probability
  3. Enter the proper degrees of freedom
  4. Click the Input Constant radio button
  5. Enter the area to the left of the critical value into the Input Constant box. Minitab always takes the area to the left, so you'll have to adjust if you're not working with a left tail already.
    1. If you have a left tail test, this is α. For example, if your significance level was 0.10, then you would enter 0.10 into the box.
    2. If you have a right tail test, this is 1-α. For example, if your significance level was 0.10, then you would enter 0.90 into the box.
    3. If you have a two tail test, then you need to repeat this whole process two times. The first time, use α/2 for the area on the left and 1-α/2 for the area on the right. For example, if your significance level was 0.10, then there would be half of that (0.05) on each side. The first time through, you would use 0.05 and the second time through you would use 0.95.
  6. Click OK

Finding the Test Statistic, P-value, and Confidence Interval (Questions 14-16)

  1. Go to Stat / Basic Statistics / 1-Sample t
  2. Select mass as your variable to test
  3. Enter the claimed mean in the "test mean" box
  4. Go into options
    1. The confidence interval should agree with your significance level. If your significance level is 0.10 (10%), then your confidence level should be 90%.
    2. Make sure the alternative hypothesis is set properly for your problem.
    3. Click OK
  5. Click OK

Notice how the summary statistics are given. You didn't have to do a separate step in question 6 to find them, they're given here. However, we wanted to check for normality, so it was a good thing we did question 6.

Changing to a One-Tail Test (Question 24)

  1. Repeat the section above, but under options, change the alternative to be a greater than.
  2. Click OK

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Last updated Jan 5, 2007 1:37 PM