Transcript Reliability: Internal Consistency

Reliability:
Internal Consistency
By Lynn Woolever
AED 615
October 23, 2006
Internal Consistency
Reliability refers to the consistency of
scores obtained in an experiment.
Specifically, the internal consistency
method refers to the consistency of
scores using only a single
administration of an instrument.
Types of Internal Consistency
There are three major types of internal
consistency testing:
Split-half Procedure
Kuder-Richardson Approach
Alpha Coefficient
Split-Half Coefficient
In this procedure, the test is split in half
and each half is scored separately–
usually odd items versus even items. A
coefficient is then calculated to
determine if the two halves showed the
same results. A coefficient is the
degree to which the two halves of the
test have the same results.
Split-half coefficient
Calculated using the Spearman-Brown
prophecy formula
Reliability of
scores on total test
=
2 x coefficient
1 + coefficient
Kuder-Richardson Approach
Most frequently employed method
Reliability with this test should be .70 or
higher
The number of items, the mean, and
the standard deviation are needed
Typically use K 20 or K 21
Kuder-Richardson Approach
K = number items, M = mean, SD =
standard deviation
K 21
Reliability = K
1 – M(K – M)
coefficient
K-1
K(SD2)
Alpha Coefficient
This used to calculate the reliability of
items that are not scored right or wrong
such as an essay test where more than
one answer is possible.
Form of the K 20
Value of reliability and validity
If the research survey is either not valid
or reliable then the research won’t be
valid or reliable.
Without valid or reliable research
credibility of the study is in question.
Use in Quantitative Research
Gives reliability and validity numbers to
support the quantitative research and
thereby increase credibility of the study.
Use in Qualitative Research
Because these studies often describe
situations, instead of reliability and
validity, researchers rely on honesty,
believability, expertise, and integrity to
prove the credibility of the study.
Journal Article
One JAE article that uses Reliability and
Validity is:
Statistical Procedures Employed in
the Journal of Agricultural
Education.
http://pubs.aged.tamu.edu/jae/pdf/vol31/
31-04-46.pdf
Journal Article
In the “Statistical Procedures Employed in
the Journal Of Agricultural Education”
article, internal reliability was used to
test the reliability of different types of
sources used in the Journal of
Agricultural Education.
Work Cited
Bowen, B., Rollins, T., Baggett, C. &
Miller, J. (1990). Statistical Procedures
Employed in the Journal of Agricultural
Education. Journal of Agricultural
Education, 31(4), 46-51.