Several Measures of Reliability with SPSS – Problem 3.4: Test-Retest Reliability Using Correlation

• Is there support for the test-retest reliability of the two visualization test scores?

Let’s do a Pearson r for visualization test and visualization retest scores.

• Click on Analyze → Correlate → Bivariate.
• Move variables visualization and visualization retest into the variable box.
• Do not select flag significant correlations because statistical significance is not important for reliability assessment; rather we should focus on the magnitude of the correlations. Reliability coefficients should be positive and greater than .70; statistical significance is not considered because we are not doing inferential statistics but instead are trying to see if our sample’s data provide evidence to support the reliability of the visualization measure.
• Click on Options.
• Click on Means and Standard deviations.
• Click on Continue and then OK. Do your syntax and output look like Output 3.4?

Output 3.4: Pearson r for the Reliability of the Visualization Score

CORRELATIONS

/VARIABLES=visual visual2

/PRINT=TWOTAIL SIG

/STATISTICS DESCRIPTIVES

/MISSING=PAIRWISE.

Correlations

Descriptive Statistics

Interpretation of Output 3.4

The first table provides the descriptive statistics for the two variables, visualization test and visualization retest. The second table indicates that the correlation of the two visualization scores is very high (r = .89) so there is strong support for the test-retest reliability of the visualization score. This correlation is significant, p < .001, but here we are not concerned about the significance because we are not doing inferential statistics; instead we are interested in the size of the relationship between the variables in this sample to see if our data support the reliability of the measure.

Example of How to Write About Problem 3.4

Method

A Pearson’s correlation was computed to assess test-retest reliability of the visualization test scores, r (75) = .89. This indicates that there is good test-retest reliability for these data.

Source: Leech Nancy L. (2014), IBM SPSS for Intermediate Statistics, Routledge; 5th edition;

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