T test for age for cases and control

[Guerraje]

Hello,

I am trying to run a t-test for age as it is continuous. I need to find the mean age and p value for age. With the code below I am able to see the overall mean age. However, I am unsure how to find the mean age of my case and control groups. I have tried using Pair statements, I have tried creating a table after the VAR and these are all giving me very different but not correct outputs. Thank you for any guidance. 

proc ttest data= work.query;

var Baseage;

run;

[ballardw · Accepted solution]

TTest wants to test your mean against a value. Typically that means a Class variable to provide two groups and the test is are the means of the group equal. So if you have a variable that indicates "case" or "control" the syntax would be to test the means between two groups. If you don't have such a variable, then add one to your data set.

proc ttest data= work.query;
   class casecontrolvariablename;
   var Baseage;
run;

To get a pvalue you must test against something.

You can provide a value to test your mean against with the H0= option on the Proc statement. For example the code below will test if your mean for the Baseage variable is 21.3 (picked at random to provide a syntax example).

proc ttest data= work.query  H0= 21.3;
   var Baseage;
run;

You should know your data and provide some value that has a use.

[Guerraje]

I added a CLASS statement to compare against my VAR Baseage and was able to get what I was looking for.

Thank you so much!