03-30-2017 04:04 AM
I am tring to understand the results I got.
My code is:
proc ttest data=sasuser.sasfile010916;
format stage firstgroup.;
var ROA1 ROA2 ROA3 ROA4 ROE1 ROE2 ROIC Q LNQ ;
I copmare between the mean of group 1 to the mean of the other 3 groups mean together.
The result I got for the variable ROA1: T value = 0.06 Pr = 0.94 while F value is 2.77 pr<0.0001
According to the t value, I understand that there is not difference between group 1 to the other 3 groups together. But what is the meaning of the F value here?
Thanks for any clue...
03-30-2017 10:50 AM
Generally the F test is related to whether your variances are equal. The Ttest is supposed to test if the means differ given that the variances in the two groups are similar. When the variances are not then you maybe shouldn't be using a ttest. A large F value indicates that the variances may not be equal and the p-value is the probabiity they aren't equal given some other assumptions such as normality of the data.