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15.11 ONEWAY

     ONEWAY
             [/VARIABLES = ] var_list BY var
             /MISSING={ANALYSIS,LISTWISE} {EXCLUDE,INCLUDE}
             /CONTRAST= value1 [, value2] ... [,valueN]
             /STATISTICS={DESCRIPTIVES,HOMOGENEITY}
             /POSTHOC={BONFERRONI, GH, LSD, SCHEFFE, SIDAK, TUKEY, ALPHA ([value])}

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 dependent 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:

The CONTRAST 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 CONTRAST subcommand may be given up to 10 times in order to specify different contrast tests. The MISSING subcommand defines how missing values are handled. If LISTWISE is specified then cases which have missing values for the independent variable or any dependent variable will be ignored. If ANALYSIS is specified, then cases will be ignored if the independent variable is missing or if the dependent variable currently being analysed is missing. The default is ANALYSIS. A setting of EXCLUDE means that variables whose values are user-missing are to be excluded from the analysis. A setting of INCLUDE means they are to be included. The default is EXCLUDE.

Using the POSTHOC subcommand you can perform multiple pairwise comparisons on the data. The following comparison methods are available:

The optional syntax ALPHA(value) is used to indicate that value should be used as the confidence level for which the posthoc tests will be performed. The default is 0.05.