GENMOD lines option for multiple comparison: trouble understanding output

[jb3]

Hi all,

I would like to do pairwise comparisons of cells in a contingency table. To do so, I followed the advice given here and constucted a generalized linear model that fits the poisson distribution:

data melanoma;
	input type:$13. site:$11. count;
	cards;
      Hutchinson's  Head         22
      Hutchinson's  Trunk         2
      Hutchinson's  Extremities  10
      Superficial   Head         16
      Superficial   Trunk        54
      Superficial   Extremities 115
      Nodular       Head         19
      Nodular       Trunk        33
      Nodular       Extremities  73
      Indeterminate Head         11
      Indeterminate Trunk        17
      Indeterminate Extremities  28
      ;


proc freq data=melanoma;
	weight count;
	tables type*site / chisq cellchi2 nopercent;
run;


proc genmod data=melanoma;
	class type site;
	model count=type|site / dist=poisson type3;
	slice type*site /lines;
run;

The "lines" option creates groups of cells that are not significantly different and displays them nicely in the results, e.g.:

Now what I don't understand is the meaning of the two lines with empty 'site' (rows 2 and 4) in the image above, and I can't find any explanation of these lines in the documentation or the internets. Can anyone explain to me what these two lines mean, and why line 2 dows not have any letter, but line 4 has letter B?

Thanks in advance!

J.

[lvm · Accepted solution]

Those are just blank lines. In other words, there is a blank line between each mean, presumably to "look better". There is a letter used, because one should think of the letters as "lines"

[jb3]

Thanks, that makes sense.