Single measurement point

Unlike the test-retest reliability, parallel-forms reliability and inter-rater reliability, testing for internal consistency only requires the measurement procedure to be completed once (i.e., during the course of the experiment, without the need for a pre- and post-test). This may reflect post-test only designs in experimental and quasi-experimental research, as well as single tests in non-experimental research (e.g., relationship-based research) that have no intervention/treatment [see the articles, Experimental research designs, Quasi-experimental research designs and Relationship-based research designs, if you are unsure about the differences between these different types of quantitative research design].

When faced with such a scenario (i.e., where the measurement procedure is only completed once), we examine the reliability of the measurement procedure that has been created in terms of its internal consistency; that is, the internal consistency of the different items that make up the measurement instrument. Reliability as internal consistency can be determined using a number of methods. We look at the split-half method and Cronbach's alpha:

How do I use these tests of reliability?

In order to examine reliability, a number of statistical tests can be used. These include Pearson correlation, Spearman's correlation, independent t-test, dependent t-test, one-way ANOVA, repeated measures ANOVA and Cronbach's alpha. You can learn about these statistical tests, how to run them using the statistics package, SPSS, and how to interpret and write up the results from such tests in the Data Analysis section of Lærd Dissertation.


Bartholomew, D. J. (2002). Measuring intelligence: Facts and fallacies. Cambridge: Cambridge University Press.

Cronbach, L. J. (1947). Test "reliability": Its meaning and determination. Psychometrika, 12(1): 1-16.

Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16(3): 297-334.

Kuder, G F., & Richardson, M. W. (1937). The theory of the estimation of test reliability. Psychometrika, 2(3): 151-160.

Miller, M. B. (1995). Coefficient alpha: A basic introduction from the perspectives of classical test theory and structural equation modelling. Structural Equation Modeling, 2(3): 255-273.

Ratcliff, R. (1993). Methods for dealing with reaction time outliers. Psychological Bulletin, 114(3): 510-532.

Salthouse, T. A., & Hedden, T. (2002). Interpreting reaction time measures in between-group comparisons. Journal of Clinical and Experimental Neuropsychology, 24(7): 858-872.

Schuerger, J. M., & Witt, A. C. (1989). The temporal stability of individually tested intelligence. Journal of Clinical Psychology, 45(2): 294-302.

Yellott, Jr., J. I. (1971). Correction for fast guessing and the speed-accuracy tradeoff in choice reaction time. Journal of Mathematics Psychological, 8(2): 159-199.

1 2 3