test-retest reliability and Spearman-Brown split half coefficient

Posted by Paul Mcgeoghan on Jan 25, 2007; 3:02pm
URL: http://spssx-discussion.165.s1.nabble.com/test-retest-reliability-and-Spearman-Brown-split-half-coefficient-tp1073459.html

Hi,

I have been reading a lot of websites relating to reliability and agreement this week and have a
customer who has carried out the following:

She has 9 people who answered nominal questions:
Yes, No, Don't Know
on 2 seperate occasions.
She is interested in knowing whether the respondents reliably answer the questions the same over
the 2 time periods.

She also has a number of likert questions also where the same 9 respondents answered the questions
at time 1 and time 2 and wants to see if they have reliably answered each question the same over the
2 time periods.

From what I have read, this seems to be referred to as test-retest reliability and a correlation
between each pair of questions seems to be the way to approach it.

So for the likert scale questions, I could just do a Spearman's correlation coefficient?
For the nominal questions, what can I use?

I have also seen reference to Spearman-Brown split half coefficient (Analyse Scale Reliability and
Split-Half).
Can this be used to compare each pair of questions at the 2 time intervals, and does the data have
to be likert-scale in this instance?

Hope I have explained the problem clearly.

Thanks,
Paul


==================
Paul McGeoghan,
Application support specialist (Statistics and Databases),
University Infrastructure Group (UIG),
Information Services,
Cardiff University.
Tel. 02920 (875035).