# Cronbach's alpha

## The internal consistency reliability for Likert-type response sets

Cronbach's alpha is used for calculating reliability coefficients for survey instruments that use Likert-type response sets. Cronbach's alpha coefficient ranges from 0 to 1.0 with higher values denoting increased reliability. The criterion for an acceptable Cronbach's alpha coefficient is debated in the literature, but to be conservative,

**any alpha coefficient below .75 is a cause for concern**. If at all possible, use the**standardized alpha coefficient,**which is an even more conservative method for calculating reliability.### The steps for conducting Cronbach's alpha in SPSS

1. The data is entered in a within-subjects fashion.

2. Click

3. Drag the cursor over the

4. Click on

5. Click on the first survey item to highlight it.

6. Click on the

7. Repeat Steps 5 and 6 until all of the survey items are in the

8. Click on the

9. In the

10. Click

11. Click

2. Click

**.**__A__nalyze3. Drag the cursor over the

**Sc**drop-down menu.__a__le4. Click on

**.**__R__eliability Analysis5. Click on the first survey item to highlight it.

6. Click on the

**arrow**to move the item into the**box.**__I__tems:7. Repeat Steps 5 and 6 until all of the survey items are in the

**box.**__I__tems:8. Click on the

**button.**__S__tatistics9. In the

**Descriptives**table, click on the**,**__I__tem**, and**__S__cale**Sc**boxes to select them.__a__le if item deleted10. Click

**Continue**.11. Click

**OK**.### The steps for interpreting the SPSS output for Cronbach's alpha

1. Look at the

2. Look in the

3. If the alpha coefficient was

Continue iterations until the alpha coefficient meets the criterion of .75 or all items are correlated at above .30.

If the coefficient does not approach .75, then review the items for systematic error.

**Reliability Statistics**table, in the**Cronbach's Alpha**column. This is the alpha coefficient associated with the items. It needs to be more than .75 to be acceptable.2. Look in the

**Item-Total Statistics**table, in the**Corrected Item-Total Correlation**, record every item that has a value**LESS THAN .30**.3. If the alpha coefficient was

**LESS THAN .75**and there were items with a Corrected Item-Total Correlation of**LESS THAN .30**, then delete those items and rerun the Cronbach's alpha analysis.Continue iterations until the alpha coefficient meets the criterion of .75 or all items are correlated at above .30.

If the coefficient does not approach .75, then review the items for systematic error.

Click on the

**Principal Components Analysis**button to continue.## Hire A Statistician - Statistical Consulting for Students

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