I am a biologist, and I know this is a very basic question in the psychological realm. In psychological and neuropsychological test batteries, when dealing with patients' scores, I see that the common practice is to display the t-scores and z-scores, rather than the raw score.
- why psychologists prefer t and z values rather than a raw score?
- how is that interpreted?
- a t-value and z-value in comparison to WHAT?
In any other situation, a t-statistic would be the result of comparing 2 means, and the t´s would tell me how far or close I am from the mean. Is it the same in a psychological scenario? But then again, what were the comparison values to start with? More specifically, what is a good and a bad result?