T-Test for Independent Samples by Variables
Select t-test, independent, by variables on the Basic Statistics and Tables Startup Panel - Quick tab to display the T-Test for Independent Samples by Variables dialog box, which contains two tabs: Quick and Options.
For simple data analyses, it is sometimes easier to enter the data so that each column in the data file (variable) represents the responses of one group (e.g., the data for all male respondents entered into the first column of the file, and the data for all female respondents entered into the second column). If your data are arranged in this manner, use this dialog box. Otherwise use the T-Test for Independent Samples - by Groups dialog box.
See also, the t-Test for Independent Samples Overview.
Variables (groups)
Click the Variables (group) button to display a standard variable selection dialog box. Select two lists of variables. Since this setting of the input file combo box assumes that each variable represents the data for one group, each variable (group) in the first list will be compared with each variable (group) in the second list.
Summary
Click the Summary button to compute the t-tests for independent samples and display the results in a spreadsheet. The detail and formatting of the results depends on your selections in the Options tab.
Cancel
Click the Cancel button to close the dialog box without performing any analysis and return to the Basic Statistics and Tables Startup Panel.
Select Cases
Click the Select Cases button to display the Analysis/Graph Case Selection Conditions dialog box, which is used to create conditions for which cases will be included (or excluded) in the current analysis.
More information is available in the case selection conditions' overview, syntax summary, and dialog box description.
W
Click the W (Weight) button to display the Analysis/Graph Case Weights dialog box, which is used to adjust the contribution of individual cases to the outcome of the current analysis by weighting those cases in proportion to the values of a selected variable.
Weighted moments
Select the Weighted moments check box to specify that each observation contributes the weighting variable's value for that observation.
The weight values need not be integers. This module can use fractional case weights in most computations. Some other modules use case weights as integer case multipliers or frequency values. This option is available only after you have defined a weight variable via the W option described above.
DF = W-1 / N-1
When the Weighted moments check box is selected, some statistics related to the moments (such as standard deviations and variances, skewness, kurtosis) can be based on the sum of the weight values for the weighting variable (W-1), or on the number of (unweighted) observations (N-1).
The sums (and means), and sums of squares and cross products will always be based on the weighted values of the respective observations. However, in computations requiring the degrees of freedom (such as standard deviation, t-test, etc.), the value for the degrees of freedom can either be computed as the sum of the weight values minus one, or as the number of observations minus one.
Moment statistics (except for the mean) are based on the sum of the weight values for the weighting variable when the W-1 option button is selected, and are based on the number of (unweighted) observations when the N-1 option button is selected. When the Weighted moments check box is selected, several graphics options will not be available. For more information on options for using integer case weights, see also Selecting a Weighting Variable.