BookmarkSubscribeRSS Feed
MFLoGrasso
Obsidian | Level 7

I get the feeling the following request is a lot simpler than I am making it out to be.  Assume I have a variable with a finite number of possible nominal values (A - E, for example).  According to a PROC ANOVA, there is a difference between the distribution of this variable at level 1 and at level 2.  I would like to determine which, if any, of the values occur with significantly different frequencies across the two levels, and I am just flat out stuck figuring out a simple way to program this or which PROC statements to use to move forward.

3 REPLIES 3
dagremu
Obsidian | Level 7

Apologies if I'm misreading your question, but using ANOVA with a nominal dependent variable is not appropriate. It sounds like you want to see if the distribution of values in one nominal variable differs across levels of another variable. If so, I'd use PROC FREQ and add the CHISQ option to the TABLES statement to get the Pearson Chi-Square test. To investigate how much each cell in the two-way table deviates from its expected value under the null hypothesis of no association between the two variables, you could also add the CELLCHI2 option. This would add an extra number to each cell showing (observed - expected)^2 / expected. Higher values mean greater deviation. The code would look something like this:

 

proc freq data=mydata;
  tables var1 * var2 / chisq cellchi2;
run;

 

MFLoGrasso
Obsidian | Level 7

Point taken.  I was doing a distribution analysis for many variables, nominal, ordinal, interval, and ratio, so I just did a massive ANOVA for speed's sake.

 

That said, can the cell's contribution to the chi-squared value be used in such a way to generate a p-value for its difference from the same cell value in the other level?

Rick_SAS
SAS Super FREQ

I don't know about p-values, but one procedure that analyzes a cell's contribution to the chi-square value is the CORRESP procedure. The doc has an example that shows the deviation from the expected value (under the assumption of ind... In particular, see the table "Contributions to the Total Chi-Square Statistic."

SAS Innovate 2025: Register Now

Registration is now open for SAS Innovate 2025 , our biggest and most exciting global event of the year! Join us in Orlando, FL, May 6-9.
Sign up by Dec. 31 to get the 2024 rate of just $495.
Register now!

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.

Discussion stats
  • 3 replies
  • 1825 views
  • 4 likes
  • 3 in conversation