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Reliability analysis in SPSS

Reliability analysis in SPSS

Cronbach’s alpha is a common measure of internal consistency. It is commonly used to determine if the scale is reliable or not when the questionnaire is developed based on multiple Likert scale statements.

A researcher developed a questionnaire to identify the challenges faced by students in an educational institution. Questions were developed based on the 5-point Likert scale, with responses ranging from “Strongly agree” to “Strongly disagree”. In order to determine if the questionnaire could reliably measure the latent variable, i.e., challenges faced by students, the Cronbach’s alpha test was conducted. The acceptable reliability value is 0.6. Therefore, a questionnaire is considered reliable if its reliability value is more than 0.6.

In SPSS, reliability analysis is found in Analyze > Scale > Reliability Analysis

We would then get ‘Reliability Analysis’ dialog box.

All questions that are to be checked for reliability are transferred to the ‘Items’ box.

In the statistics option, click on ‘Scale if item deleted’ under the ‘Descriptives for’ group.

Click on ‘Continue’ and ‘Ok’.

Output of reliability analysis test

Reliability statistics table gives the value for Cronbach’s alpha. Here, the Cronbach’s alpha value is equal to 0.844 and hence the questionnaire is considered as reliable. 

Then, we will get the ‘Item-Total Statistics’ table.

The value for ‘Cronbach’s Alpha if Item Deleted’ is found in the final column. This column presents the probable Cronbach’s Alpha value if that particular item is deleted from the scale.

The above table shows that the lowest corrected item total correlation for Q8 (0.088) might reduce the overall reliability. The ‘Cronbach’s Alpha value if item deleted’ score of 0.881 is a further evidence. The general rule is that if any statement has ‘Cronbach’s Alpha value if item deleted’ more than the existing total Cronbach’s Alpha value, then it should be eliminated.

Data: Reliability Analysis_Data.sav

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