Hi, I haven't yet tried using your function, I will rate it after I have used it. However I was wondering if somebody could explain to me whether it is possible for me to perform the following analyses with this function: (1) a priori contrasts (2 tailed) comparing mean scores between phase 1 vs phase 2 of experiment, then if that contrast comes out significant (2) examine the day X phase interaction term (each "Phase" has 7 days in it)...Just not sure this function will allow me to look at interactions like this.
A phenomenal function for ICC--quick, painless, and complete. The only minor inconvenience is the fact that there are several functions that must be put into the code, but that is a small price to pay.
Hi, PLease can somebody comment on Lee Newmans suggested error in this function? Is it an error or not?
I think it might be as I tried the example data matrix given above (by Lee Newman) - in Arash Salarian's 2008 m file "ICC.m" with the case set to yeild chronbach's alpha - and got out -0.1235 ......
I think there may be an error in your code and therefore the function returns an incorrect value. In the last line, you have a=(N*r)/(1+(N-1)*r); I believe that instead of the 1 in the denominator, you should have vbar, where vbar is the average variance (see equation on wikipedia). I checked the results of your function versus the output of SPSS and the output of Alexandros Leontitsis's posted m-file, and your function does not produce either the correct alpha or standardized alpha (Leontitdis's function produces the correct unstandardized alpha).
2 4 2 5
7 1 3 4
7 2 4 7
4 7 2 5
6 2 6 6
1 6 2 4
3 4 2 4
7 7 2 6
6 1 2 1
7 4 4 1
SPSS Output: Alpha = -0.1235 , 0.0036 (standardized)
Leontitsis Output: cronbach(X), ans = -0.1235
Your m-file Output: cronbach(X), ans = 0.2088