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EhsanKhedive
Calcite | Level 5

I have a 3*6 (3 nitrogen rates and 6 rice varieties)  factorial design and I don't know how to make any contrast I need. Ive looked up SAS/STAT help but didn't find the answer. The questions are as follow:

comparison between Linear interaction of nitrogen with variety 6 vs. other varieties. ie. NL*(V6 vs. others). (NL means the linear interaction with Nitrogen factor).

NL*

NL*(V2 vs. V5)

NL*(V1 vs. V3 vs. V4)

Quadratic interactions are same as linear:

NQ*(V6 vs. others)

NQ*

NQ*(V2 vs. V5)

NQ*(V1 vs. V3 vs. V4)

The data are attached.

Thank you in advance

1 ACCEPTED SOLUTION

Accepted Solutions
SteveDenham
Jade | Level 19

Some comments:

PROC GLM does not correctly calculate standard errors for split plot and strip plot designs.  Let me repeat that.  PROC GLM does not correctly calculate standard errors for split plot and strip plot designs.

Get a copy of SAS for Mixed Models, 2nd ed. by Littell et al., to see code for PROC MIXED for this design, and many examples of contrasts.

If you fit your data with a mixed model, consider using LSMESTIMATE statements (either in PROC GLIMMIX or PROC PLM), and it becomes straightforward to compare lsmeans of interest.

Steve Denham

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2 REPLIES 2
SteveDenham
Jade | Level 19

Some comments:

PROC GLM does not correctly calculate standard errors for split plot and strip plot designs.  Let me repeat that.  PROC GLM does not correctly calculate standard errors for split plot and strip plot designs.

Get a copy of SAS for Mixed Models, 2nd ed. by Littell et al., to see code for PROC MIXED for this design, and many examples of contrasts.

If you fit your data with a mixed model, consider using LSMESTIMATE statements (either in PROC GLIMMIX or PROC PLM), and it becomes straightforward to compare lsmeans of interest.

Steve Denham

EhsanKhedive
Calcite | Level 5

Thank you very much, I found my way out with this book.

Best Regards

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