If your interest is reliability then you don't need to do any statistical
"comparisons". What you are describing is a case for generalizability theory
in which you use the data to estimate the variance components and then
estimate what the reliability would be if you vary the number of trials.
Books by Brennan and Shavelson & Webb or the original by Cronbach et al
would be helpful.
Cronbach, L., Gleser, G., Nanda, H. & Rajaratnam, N. (1972). The
dependability of behavioral measurements. New York: Wiley.
Brennan, R. (1983). Elements of generalizability theory. Iowa City, IA:
American College Testing Program.
Shavelson, R. $ Webb, N. (1991). Generalizability Theory: A primer. Newbury
Park, CA: Sage.
Paul R. Swank, Ph.D.
Professor
Developmental Pediatrics
UT Houston Health Science Center
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Clark Dickin
Sent: Monday, July 23, 2001 10:08 PM
To: [EMAIL PROTECTED]
Subject: Interclass Correlation??
I am trying to determine the reliability of a balance test for individuals
with Alzheimer's disease. The test involves six different conditions, with
each condition consisting of three trials (6 x 3). Each individual has
performed the complete test twice, which gives me 6 trials for each of the 6
conditions. I would like to determine at what point the individuals
performance becomes reliable (stable). Specifically I want to know how many
trials need to be performed in order to determine when the individual has
move beyond learning and into actual performance.
Specifically, my questions are:
(1) whether or not an ICC is the appropriate test to perform,
(2) if the ICC is appropriate do I need to calculate an ICC for each set of
two consecutive trials or for the entire group of 6 trials for each
condition of the six condition test, and
(3) Do I need to correct the alpha level to accommodate for the multiple
comparisons (.05/# of contrasts)?
Any help would be appreciated.
Clark Dickin
[EMAIL PROTECTED]
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