12.6 ONEWAY

     ONEWAY
             [/VARIABLES = ] var_list BY var
             /MISSING={ANALYSIS,LISTWISE} {EXCLUDE,INCLUDE}
             /CONTRASTS= value1 [, value2] ... [,valueN]
             /STATISTICS={DESCRIPTIVES,HOMOGENEITY}
     

The ONEWAY procedure performs a one-way analysis of variance of variables factored by a single independent variable. It is used to compare the means of a population divided into more than two groups.

The variables to be analysed should be given in the VARIABLES subcommand. The list of variables must be followed by the BY keyword and the name of the independent (or factor) variable.

You can use the STATISTICS subcommand to tell PSPP to display ancilliary information. The options accepted are:

• DESCRIPTIVES Displays descriptive statistics about the groups factored by the independent variable.
• HOMOGENEITY Displays the Levene test of Homogeneity of Variance for the variables and their groups.

The CONTRASTS subcommand is used when you anticipate certain differences between the groups. The subcommand must be followed by a list of numerals which are the coefficients of the groups to be tested. The number of coefficients must correspond to the number of distinct groups (or values of the independent variable). If the total sum of the coefficients are not zero, then PSPP will display a warning, but will proceed with the analysis. The CONTRASTS subcommand may be given up to 10 times in order to specify different contrast tests.