12-01-2015 10:18 AM
I tested 4 different sugar solutions in 20 healthy volunteers. They had to drink the solutions until they were satiated.
So my question is: Is there a significant difference in drinking time between the 4 solutions?
I want to analyze it with SAS, but I'm not sure which syntax to use. I've already run ANOVA, but the resulting p-value is not consistent with the p-value I found using GraphPad Prism. I think it's because SAS did a normal ANOVA, but it has to be a repeated measures ANOVA with multiple comparisons.
I tried a lot of different commands in SAS, but I'm not sure which one is the right one. So if anybody could help me? Would be nice
12-01-2015 12:16 PM
You say you think it should be a repeated measures analysis, but there's nothing in your decription that indicates repeated measures was actually performed. You said: "I tested 4 different sugar solutions in 20 healthy volunteers. They had to drink the solutions until they were satiated."
So can you explain further?
12-02-2015 08:30 AM
Yes, so, these 20 volunteers all tested the 4 different solutions at different study days. So that's why it is repeated (with the same subjects and the same solutions for every subject).
12-02-2015 08:23 AM
You are right that you have dependent data because "time to satiety" will partly depend on the person.
RM ANOVA is one way to analyze such data, and it can be done in SAS, but RM ANOVA makes rather strong assumptions (it assumes sphericity) and a better way to analyze such data is with multilevel models. Since your DV is continuous, then PROC MIXED is probably a good place to start.