EMMEANS Subcommand (UNIANOVA command)

EMMEANS displays estimated marginal means of the dependent variable in the cells (with covariates held at their overall mean value) and their standard errors for the specified factors. Note that these are predicted, not observed, means. The estimated marginal means are calculated using a modified definition by Searle, Speed, and Milliken (1980).

  • TABLES, followed by an option in parentheses, is required. COMPARE is optional; if specified, it must follow TABLES.
  • Multiple EMMEANS subcommands are allowed. Each is treated independently.
  • If identical EMMEANS subcommands are specified, only the last identical subcommand is in effect. EMMEANS subcommands that are redundant but not identical (for example, crossed factor combinations such as A*B and B*A) are all processed.

TABLES(option). Table specification. Valid options are the keyword OVERALL, factors appearing on the factor list, and crossed factors constructed of factors on the factor list. Crossed factors can be specified using an asterisk (*) or the keyword BY. All factors in a crossed factor specification must be unique.

  • If OVERALL is specified, the estimated marginal means of the dependent variable are displayed, collapsing over factors.
  • If a factor, or a crossing of factors, is specified on the TABLES keyword, UNIANOVA collapses over any other factors before computing the estimated marginal means for the dependent variable.
  • The TABLES keyword may be followed by the WITH keyword and a parenthesized list of covariates and values. Tables are produced with the values of the covariates fixed at the specified values. The keyword MEAN causes the covariate to be fixed at its observed mean value.

COMPARE(factor) ADJ(method). Main- or simple-main-effects omnibus tests and pairwise comparisons of the dependent variable. This option gives the mean difference, standard error, significance, and confidence interval for each pair of levels for the effect specified in the TABLES command, as well as an omnibus test for that effect. If only one factor is specified on TABLES, COMPARE can be specified by itself; otherwise, the factor specification is required. In this case, levels of the specified factor are compared with each other for each level of the other factors in the interaction.

  • The optional ADJ keyword allows you to apply an adjustment to the confidence intervals and significance values to account for multiple comparisons. Methods available are LSD (no adjustment), BONFERRONI, or SIDAK.
  • If OVERALL is specified on TABLES, COMPARE is invalid.

Example

UNIANOVA DEP BY A B
  /EMMEANS = TABLES(A*B) WITH(X=1.0) COMPARE(A) ADJ(LSD)
  /DESIGN.
  • The output of this analysis includes a pairwise comparisons table for the dependent variable DEP.
  • Assume that A has three levels and B has two levels. The first level of A is compared with the second and third levels, the second level with the first and third levels, and the third level with the first and second levels, with the value of the covariate X fixed at 1.0. The pairwise comparison is repeated for the two levels of B.