If your dissertation uses a questionnaire, rating scale, or any multi-item instrument, your supervisor will ask about Cronbach's alpha. This guide explains what it is, what score you need, and exactly how to report it in APA 7th Edition format.
What is Cronbach's alpha?
Cronbach's alpha measures the internal consistency of a scale — how much all the items in your questionnaire are measuring the same underlying construct. It ranges from 0 to 1. A higher score means the items are more consistent with each other.
Think of it this way: if you have 10 questions all measuring "employee satisfaction", a high alpha means respondents who scored high on question 1 also tended to score high on questions 2 through 10. The questions are pulling in the same direction.
What alpha score do you need?
The standard interpretation scale used in academic research:
- 0.90 and above — Excellent
- 0.80 to 0.89 — Good
- 0.70 to 0.79 — Acceptable
- 0.60 to 0.69 — Questionable
- Below 0.60 — Poor (may need to revise or remove items)
Most supervisors accept 0.70 as the minimum threshold for a usable scale. Anything below 0.60 requires explanation or instrument revision.
How to report Cronbach's alpha in APA 7th Edition
The APA format is: alpha value, interpretation, number of items
Example:
alpha = .84 (Good internal consistency, k = 12 items)
Note: APA convention drops the leading zero before the decimal point for values that cannot exceed 1.0. Write .84 not 0.84.
Item-total correlations and alpha-if-deleted
Beyond the overall alpha, you should also check:
Item-total correlations — the correlation between each individual item and the total scale score. Items below 0.30 may be poorly worded or measuring something different from the rest of the scale.
Alpha if item deleted — what the overall alpha would be if you removed each item. If removing a particular item substantially increases alpha, that item is weakening your scale and you should consider removing it.
How to get these results automatically
ResearchScope (bizscope.space/research) computes Cronbach's alpha, item-total correlations, and alpha-if-deleted for all detected Likert items automatically. Upload your CSV and the reliability results appear instantly, formatted in APA format ready to copy into your Chapter 4.
The Student plan ($6.99 / 7-day pass) includes the full item analysis table in the PDF report.
What to write in your dissertation
A standard reliability paragraph looks like this:
"The internal consistency of the scale was assessed using Cronbach's alpha. The results indicated good reliability (alpha = .84, k = 12 items). All item-total correlations exceeded .30, suggesting that all items were adequately contributing to the overall scale."
If an item was removed: "Item Q7 was removed as it exhibited a low item-total correlation (r = .18) and its removal increased alpha from .76 to .81."