Statistics anyone here?

Question

Here is some statistics from a study.

Mean = 13

standard deviation = 3.3

Subjects (n) = 24

Given the above stats, what would be considered statistically different from mean of 13 at 95% CI? Can you use formula sigma/SQRT of n * Z1-a/2?

Answer 1

You can use that formula, as long as you assume that the standard deviation is known (ie the REAL standard deviation is 3.3, not just the standard deviation of your sample).  In that case your 95% CI is

(13 - 1.96*3.3/sqrt(24) ; 13 + 1.96 * 3.3/sqrt(24))  (1.96 is your Z(1-a/2) for a = 5%)

If the population variance is UNKNOWN, then you will have to use the t-distribution instead of the normal distribution.  If you haven't heard of that, chances are you're just meant to use the normal anyway.