T-Test for Single Means - Advanced tab
Select the Advanced tab of the T-Test for Single Means dialog box to access options to specify the reference value to use when performing a t-test for single means as well as to visualize the distribution of the variable using a variety of plots.
Summary: T-tests
Click this button to compute the t-tests for single means and display the results in a spreadsheet.
The detail and formatting of the results depend on the selections made on the Options tab.
Reference values
When more than one variable has been selected via the Variables button, use the options in the Reference values group box to specify whether to test all variables against the same hypothesized mean, or to test each variable against a different (user-specified) mean.
Test all means against
Select this option button and specify the reference value in the corresponding edit field to test each variable against the same reference value (or hypothesized mean).
This option performs a separate test for each variable. To test the hypothesis that the means for all variables are equal, use ANOVA/MANOVA.
Test means against different user-defined constants
Select this option button to specify different reference values for each t-test (or variable). Click the Specify button (see description below) to enter the values.
Specify
- Click this button to display the Select reference values dialog box.
- Use the options to specify a separate reference value for each selected variable.
The Test means against different user-defined constants option button must be selected for this button to be available.
Histograms
Click this button to produce a cascade of histograms (one for each selected variable), summarizing the distribution of the respective variable.
Box & whisker plot
Click this button to produce a box and whisker plot for the selected variables.
- First, the Box-Whisker Type dialog box is displayed, which contains options to specify a box and whisker type plot to use.
- Then, one box plot for each variable is produced.
Box and whisker plots summarize the distribution of the dependent variable. Specifically each variable is represented by one box and whisker component, which is made up of three parts:
- A central line to indicate central tendency or location
- A box to indicate variability around this central tendency
- Whiskers around the box to indicate the range of the variable
Probability plots
Probability plots are used to determine whether a variable can be fit with the normal distribution.
Three types of probability plots can be selected in this group box:
Normal
Click this button to produce a cascade of normal probability plots for the selected variables.
Half-normal
Click this button to produce a cascade of half-normal probability plots for the selected variables.
Detrended
Click this button to produce a cascade of detrended normal probability plots for the selected variables.
p-value for highlighting
The default p-value for highlighting is .05.
You can adjust this p-value by entering a new value in the edit box or using the microscrolls.
For more details on p-value, see Elementary Concepts.