EMMEANS Subcommand (MIXED command)

EMMEANS displays estimated marginal means of the dependent variable in the cells and their standard errors for the specified factors. Note that these are predicted, not observed, means.

  • The TABLES keyword, 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 by 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 all factors.
  • If a factor, or a crossing factor, is specified on the TABLES keyword, MIXED will compute the estimated marginal mean for each level combination of the specified factor(s), collapsing over all other factors not specified with TABLES.

WITH (option).

Covariate values. Valid options are covariates appearing on the covariate list on the VARIABLES subcommand. Each covariate must be followed by a numeric value or the keyword MEAN.

  • If a numeric value is used, the estimated marginal mean will be computed by holding the specified covariate at the supplied value.
  • When the keyword MEAN is used, the estimated marginal mean will be computed by holding the covariate at its overall mean. If a covariate is not specified in the WITH option, its overall mean will be used in estimated marginal mean calculations.

COMPARE(factor) REFCAT(value) ADJ(method). Main- or simple-main-effects omnibus tests and pairwise comparisons of the dependent variable. This option gives the mean difference, standard error, degrees of freedom, significance, and confidence intervals for each pair of levels for the effect specified in the COMPARE keyword, and 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.
  • By default, all pairwise comparisons of the specified factor will be constructed. Optionally, comparisons can be made to a reference category by specifying the value of that category after the REFCAT keyword. If the compare factor is a string variable, the category value must be a quoted string. If the compare factor is a numeric variable, the category value should be specified as an unquoted numeric value. Alternatively, the keywords FIRST or LAST can be used to specify whether the first or the last category will be used as a reference category.

Example 

MIXED Y BY A B WITH X
  /FIXED A B X
  /EMMEANS TABLES(A*B) WITH(X=0.23) COMPARE(A) ADJ(SIDAK)
  /EMMEANS TABLES(A*B) WITH(X=MEAN) COMPARE(A) REFCAT(LAST) ADJ(LSD).
  • In the example, the first EMMEANS subcommand will compute estimated marginal means for all level combinations of A*B by fixing the covariate X at 0.23. Then for each level of B, all pairwise comparisons on A will be performed using SIDAK adjustment.
  • In the second EMMEANS subcommand, the estimated marginal means will be computed by fixing the covariate X at its mean. Since REFCAT(LAST) is specified, comparison will be made to the last category of factor A using LSD adjustment.