To correct this, open the graph to edit it. The bounds are incorrect, as Minitab uses the three values in each treatment as three separate observations. The graph you get should look something like this, but it is not correct: Use Graph > Interval Plot > One Y With Groups.įor the Graph variables enter Value for the Categorical variables for grouping, enter Treatment. The first column is the treatment group, the second column indicates which value is included (this helps with checking), and the third column provides the numerical value. To plot the confidence intervals of interest, the estimates and confidence interval bounds are entered into a Minitab worksheet, as shown below. A model was fitted to provide estimates of the mean number of seeds harvested in each of four treatment conditions this model adjusted for covariates. The data are from a study of ways of harvesting seeds from native lilies. If your confidence intervals are symmetric, meaning that the form is (point estimate +/- margin of error), follow the example here.
By 'trick', we mean exploiting what is possible in Minitab, without it being a direct Minitab feature. You can plot confidence intervals for other estimates, perhaps from more complex models, in Minitab, but this involves some tricks. Minitab can provide confidence intervals for means, for example, via the Graphs > Interval Plot menu.Ĭonfidence intervals for pairwise comparisons of means from a General Linear Model can be obtained via Stat > ANOVA > General Linear Model > Comparisons.
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