# The Difference between Two Means

## Formatting Data for Computer Analysis

Most computer programs that compute $t$ tests require your data to be in a specific form. Consider the data in Table 2.

Table 2. Example Data.

Group 1 Group 2
3 2
4 6
5 8

Here there are two groups, each with three observations. To format these data for a computer program, you normally have to use two variables: the first specifies the group the subject is in and the second is the score itself. The reformatted version of the data in Table 2 is shown in Table 3.

Table 3. Reformatted Data.

G Y
1 3
1 4
1 5
2 2
2 6
2 8

To use Analysis Lab to do the calculations, you would copy the data and then

1. Click the "Enter/Edit Data" button. (You may be warned that for security reasons you must use the keyboard shortcut for pasting data.)
4. Set the Dependent Variable to $\mathrm{Y}$.
5. Set the Grouping Variable to $\mathrm{G}$.
6. Click the "$t$-test/confidence interval" button.
The $t$ value is $-0.718$, the $df = 4$, and $p = 0.512$.