Minitab Notes for Activity 5

Creating the Worksheet

  1. Label the first column sample mean
  2. Enter the sample means into the first column

Generating a Histogram (Question 7)

  1. Go to Graph / Histogram
  2. Select the sample mean as the X variable
  3. (Optional: Recommended) Change the formatting on the bars of the histogram. By default, the bars are not shaded, so it can be difficult to see them. You can change that by following these steps.
    1. Highlight the "Bar" from Item 1
    2. Click Edit Attributes
    3. Click on the pull down menu for Fill Type and choose Right Slant (or some other type of fill)
    4. You can also change colors of the bars if you like
    5. Click OK
  4. (Optional: Recommended) Change the number of bars. Minitab will probably pick too many bars for the graph to be useful. You may want to see what it does and then go back and play with the graphs until you get one that looks nice
    1. Click Options
    2. Choose Number of intervals for the Definition of Intervals
    3. Enter the number of bars. Choosing an odd number like 7 is probably a good starting point. Play with different values until you get a good looking graph.
    4. Click OK
  5. (Optional) You can add titles to your graph by choosing the Title option from the Annotation pull down menu.
  6. Click OK to generate the graph.

Checking Normality (Questions 8 and 9)

Up until this point, we've been using the probability plot command under graphs to check normality. I like this graph as it has confidence intervals bands on it that give you a slightly better idea of whether the data follows the line or not. However, we can do both the normal probability plot and the Anderson-Darling test at one time if we choose another option, so that's what we're going to do here.

  1. Go to Stat / Basic Statistics / Normality Test
  2. Select sample mean as the variable
  3. Click OK

The graph window includes both the normal probability plot and the p-value for the Anderson-Darling test.

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Last updated January 7, 2003 9:35 PM