Depends on whether you consider a lack of item homogeneity as unreliability
or not. If your content is supposed to be homogeneous then a lack of
homogeneity implies your test has problems. If your content is not
necessarily homogeneous then the reduced alpha appears to say that your
test is unreliable when that's not actually the case. All reliability
coefficients suffer from the same problem. They are all sensitive to a lack
of reliability and something else. Test retest is sensitive to trait
instability, alternate forms is sensitive to a lack of parallelness, split
half is sensitive to the bad split, and alpha is sensitive to lack of item
homogeneity. It's like any statistical model. If the model isn't
appropriate, the result is misleading.
At 07:47 PM 4/17/00 -0400, you wrote:
>At 04:26 PM 4/17/00 -0500, Paul R Swank wrote:
>>I disagree with the statement that the split-half reliability coefficient
>>is of no use anymore. Coefficient alpha, while being an excellent estimator
>>of reliability, does have one rather stringent requirement. The items must
>>be homogeneous.
>
>i don't ever seem to recall the coefficient alpha .. REQUIRES homogeneous
>content ... but rather, the SIZE of it will be impacted BY item homogeneity
>
>
>
>
>
>===========================================================================
>This list is open to everyone. Occasionally, less thoughtful
>people send inappropriate messages. Please DO NOT COMPLAIN TO
>THE POSTMASTER about these messages because the postmaster has no
>way of controlling them, and excessive complaints will result in
>termination of the list.
>
>For information about this list, including information about the
>problem of inappropriate messages and information about how to
>unsubscribe, please see the web page at
>http://jse.stat.ncsu.edu/
>===========================================================================
>
------------------------------------
Paul R. Swank, PhD.
Advanced Quantitative Methodologist
UT-Houston School of Nursing
Center for Nursing Research
Phone (713)500-2031
Fax (713) 500-2033
===========================================================================
This list is open to everyone. Occasionally, less thoughtful
people send inappropriate messages. Please DO NOT COMPLAIN TO
THE POSTMASTER about these messages because the postmaster has no
way of controlling them, and excessive complaints will result in
termination of the list.
For information about this list, including information about the
problem of inappropriate messages and information about how to
unsubscribe, please see the web page at
http://jse.stat.ncsu.edu/
===========================================================================
