One sample t -intervals

For this example the data is in column C1, titled “data.”

Begin by accessing the “1-Sample t” command.

Then you get the following.

All you need is to tell Minitab which column is the sample data.

The Options button is essential. This is where you set the confidence. The Graphs button is optional (you can obtain graphs other ways).

Options button	Graphs button

After OKing, you get results in the Session window. For the data in column C1 the text results are below. (The graphs are not shown.) Notice that the confidence is reported.

One-Sample T: data

Variable   N       Mean     StDev   SE Mean          90% CI

data      24  -0.036807  1.184664  0.241818  (-0.451253, 0.377639)

Normal Probability Plots

To obtain a normal probability plot of the sample data use the “Normality Test” command.

Specify the column of data. Don’t monkey around with the “Percentile lines” or “Tests for Normality” unless you know what you are doing.

A probability plot for the data in C1 looks like this:

To interpret this plot, begin by ignoring the line. Ask yourself, would a line fit the plot pretty well, or is there some other simple curve that would do much better? If “a line” is your answer, then (outside of outliers) the sampled data is nearly normal.