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Obsidian | Level 7

# How do I do slice test for effects when interaction is significant in 2 X 2 factorial

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Dear SIr/Ma,

I had tried to analyse a 2 X2 factor experiment with PROC GLM. I reported the P-values for A, B and AB interaction.

My SAS syntax was of this fashion:

proc univariate plot normal;
title 'Trial4Digest';
var v1;
run;
Proc GLM Order = Data;
Class A B;
Model v1 = block A B A*B;
LSmeans A*B/TDIFF PDIFF P STDERR Adjust=tukey;
Run;
Quit;

1. Where interaction was NOT SIGNIFICANT, I had used the simple effect of each factor to compare my means and report in result and discussion.

2. Where interaction was SIGNIFICANT and either FActor A or B is Sig, or FActor A or B is NOT SIGNIFICANT, i had used tukey test to assign "abcd" to the means for comparisons.

 A1 A2 P-values 3Parameter B- B+ B- B+ SEM A B A*B Ac 58.4 51.5 54.2 55.7 0.71 0.86 0.02 ˂0.01 Pro 20.5b 23.3a 22.5a 23.2a 0.39 0.07 <0.01 0.05 Bu 15.5 18.8 17.5 15.8 0.37 0.40 0.19 ˂0.01 Bra 3.66 3.96 3.80 3.30 0.10 0.19 0.54 0.04 Val 1.95b 2.39a 1.98b 2.00b 0.06 0.02 <0.01 0.01 Ap 3.03a 2.25b 2.46b 2.43b 0.09 0.175 0.01 0.01

This is the response of the reviewer:

" The use of Tukey's test to separate means is incorrect. Actually, it is not acceptable to use two statistical tests to show a difference between treatments (treatments and interaction effects and mean separation). I greatly discourage the authors from using mean separation when the effect of treatment (factor A, factor B and interaction) is displayed in the tables. A slice test can be used when the interaction is observed. Therefore Tables and text (where appropriate) should be corrected".

I do not have a clue on the way forward on using this slice test and how to interpret the subsequent result. Any help to modify my syntax and report correctly will be appreciated.

1 ACCEPTED SOLUTION

Accepted Solutions
Diamond | Level 26

## Re: How do i slice significant interaction in 2X2 factorial

There is a SLICE= option in the LSMEANS statement, that sounds like what you want.

https://documentation.sas.com/?docsetId=statug&docsetTarget=statug_glm_syntax10.htm&docsetVersion=15...

--
Paige Miller
Diamond | Level 26

## Re: How do i slice significant interaction in 2X2 factorial

There is a SLICE= option in the LSMEANS statement, that sounds like what you want.

https://documentation.sas.com/?docsetId=statug&docsetTarget=statug_glm_syntax10.htm&docsetVersion=15...

--
Paige Miller
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