What should I do when my Cronbach's alpha is low?

A Troubleshooting Checklist for Low Cronbach's Alpha

You run a reliability analysis, and the Cronbach's alpha for one of your scales comes out lower than expected. Before you panic or start deleting items, work through the likely causes in order. This blog gives you a step-by-step checklist. For a full guide to running and reading the analysis in SPSS, see our earlier post, How do I run and interpret Cronbach's alpha in SPSS?

Step 1: Check Your Data Entry:

  • Look at the frequencies for each item. Values outside the scale range, such as a 9 on a 1 to 5 scale, point to entry errors or missing value codes that were not defined.
  • Make sure missing value codes are set in Variable View so SPSS does not treat them as real answers.

Step 2: Check Reverse-Coded Items:

  • Negatively worded items must be reversed before calculating alpha.
  • A quick sign of a problem is a negative corrected item-total correlation, or a negative value in the inter-item correlation matrix.
  • After recoding, run the analysis again using the recoded variables, not the originals.

Step 3: Check You Have the Right Items:

  • Confirm that you included only the items belonging to that scale or subscale, and none from other scales.
  • If the scale has subscales, calculate alpha for each subscale separately.

Step 4: Look at the Item Statistics:

  • Review the corrected item-total correlations. Items with very low values fit poorly with the rest.
  • Look at "Cronbach's Alpha if Item Deleted" to see whether removing a particular item would noticeably improve alpha.
  • Before removing anything, read the item again. Is it ambiguous, double-barrelled or poorly translated?

Step 5: Consider the Scale Itself:

  • Scales with very few items often have lower alpha values. For these, the mean inter-item correlation can be more informative.
  • If items seem to capture more than one idea, run an exploratory factor analysis to examine the structure.

Step 6: Decide and Report:

  • Remove an item only when there is both a statistical and a conceptual reason, and report the change.
  • If alpha remains low after checking everything, report it honestly, interpret results for that scale with caution, and discuss it as a limitation.

A low alpha is often caused by simple, fixable issues such as data entry errors or missed reverse coding. Work through the checklist in order, make changes only when you can justify them, and report your decisions openly.