When I request post-hoc tests for a one-way ANOVA using ONEWAY, one of the ouput sections is "Homogeneous Groups". The bottom row of these tests is often (e.g., Tukey HSD, REGWF and REGWR, but not for Tukey B) labeled "Sig.", which in SPSS always indicates a "significance level." When this row is displayed, it often has different values for each homogeneous group and the values are generally > 0.05.
What is this "Sig." row and how am I to interpret it?
It may help to see this. Any "homogeneous groups" output will do, like: http://web.pdx.edu/~newsomj/da1/ho_ANOVA%20example.pdf (at the bottom of page 2 you can see these "Sig." values are 1.0, although clearly group 2 differs from groups 1 and 3). Or here's David Howell mentioning that he doesn't know what "Sig" means here: http://www.uvm.edu/~dhowell/gradstat/psych341/lectures/AnovaReviewFolder/class2.html (Howell wrote the statistics book I use with my students).
I have consulted the SPSS manual (BASE and ALGORITHMS) and over a dozen SPSS ONEWAY tutorials but none of them has answered this question. Many skip over homogeneous groups entirely and I take it that some people consider this output less important than the multiple comparisons output, which is a fair point, but I need to find some explanation for this "Sig." row.