Hi All,

Thank you so much for interest and input, it's great having a forum like this to discuss these sometimes tricky questions!

To give you some more clarity on the research question I am trying to answer, I am aiming to find out whether or not there is a difference in level of cognitive function (as assessed using the Mini-Mental State Exam (MMSE) between those who did/did not receive an anxiety disorder diagnosis.

I thought the most obvious way to do this was via a t-test, but you have brought up some good points that the MMSE might be an ordinal level of data. I did some quick searching on Google and found this: http://pb.rcpsych.org/content/30/9/354.3 which suggests that MMSE scores should be treated as ordinal.

If this is the case would I therefore use a Wilcoxon test instead? And if so, does that mean that the normality assumption is not as important?

Also, if someone could expand on why the MMSE scores would be seen as ordinal rather than interval data, that would be much appreciated. I have seen a number of papers treat it as interval data so it would be great to get some clarity on this.

Thanks!