I merged two datasets, a pre and post, but due to a small post size compared to the pre, I am treating the data as two independent samples and am aiming to run a ttest: data prepostindep; set pre post; run; I need to test the difference between the mean of a scale that was created by: meanscale1pre=mean (of q5 q6 q7a q8 q9 ); *data that came from pre dataset meanscale1post=mean (of q5p q6p q7ap q8p q9p); *data that came from post dataset Because it is the mean of scale data that I am testing between the two groups, the proc ttest statement doesn't work. I tried running proc genmod but go this error: ERROR: No valid observations due to invalid or missing values in the response, explanatory, offset, frequency, or weight variable. Possibly due to the fact that there are missing values for both pre and post since post only has variables that end in p (shown above), while pre doesn't and vice versa. In addition, the sample size for post is about 50 whereas it's 400 for the pre. That may change as we receive more posts in the future. What's the best way to analyze this?
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