Free tool · Chapter 3
Cronbach's alpha calculator
Paste the responses from your pilot test and get the reliability of your questionnaire — with a paragraph ready for Chapter 3.
One respondent per row, one question per column — copy straight from Excel, Google Sheets or SPSS. A header row is skipped automatically. The example shows 10 respondents and 5 questions.
10 respondents · 5 items · 1 non-number row skipped
Cronbach's alpha (α)
0.940
excellent reliability
5 items · 10 respondents
Alpha if item deleted
- Item 1: 0.912
- Item 2: 0.922
- Item 3: 0.947
- Item 4: 0.928
- Item 5: 0.920
For your Chapter 3
The reliability of the instrument was tested through a pilot study involving 10 respondents. Internal consistency across the 5 items was measured with Cronbach's alpha, which gave a coefficient of 0.94. Following George and Mallery (2003), this indicates excellent reliability, so the instrument was considered reliable for the study.
The Cronbach's alpha formula
α = k / (k − 1) × (1 − Σσ²ᵢ / σ²ₜ)
- k — the number of questions (items)
- σ²ᵢ — the variance of each question's scores
- σ²ₜ — the variance of respondents' total scores
When questions measure the same idea, respondents who score high on one tend to score high on the others, so total scores vary more than the questions do individually — and alpha rises towards 1.
How to interpret your alpha
| Cronbach's alpha | Reliability |
|---|---|
| 0.90 and above | Excellent |
| 0.80 – 0.89 | Good |
| 0.70 – 0.79 | Acceptable |
| 0.60 – 0.69 | Questionable |
| 0.50 – 0.59 | Poor |
| Below 0.50 | Unacceptable |
Rule of thumb from George and Mallery (2003), widely cited in Nigerian projects.
Writing your Chapter 3?
MonoEd drafts your methodology — instrument, validity, reliability and analysis — around your own study details. Chapters 1–2 are free; ₦6,500 once for the whole project.
Start your project freeMore free tools for your project
- Chapter 3Sample size calculatorTaro Yamane or Cochran, with the full working and a paragraph for your sampling section.
- Chapter 4Likert scale mean calculatorMean, standard deviation and accept/reject decision for each statement, as a ready table.
- Chapter 4Chi-square test calculatorχ², degrees of freedom, p-value and the decision on your hypothesis.
Common questions
What is a good Cronbach's alpha?
0.70 or higher is generally accepted as reliable for a questionnaire; 0.80 and above is good. Very high values (above 0.95) can mean some questions repeat each other.
How many respondents do I need for a pilot test?
Commonly 10–30 people who are similar to your study population but not part of your final sample. Use the same questionnaire you plan to use in the main study.
Which questions should I include?
Only the scaled questions that measure the same idea — for example, the Likert items under one research question. Leave out demographic and open-ended questions. If sections measure different things, calculate alpha for each section.
What about negatively worded questions?
Reverse-score them before pasting (on a 5-point scale, 5 becomes 1, 4 becomes 2, and so on). Otherwise they pull alpha down and the result will look unreliable.
What does 'alpha if item deleted' mean?
It shows what alpha would be without each question. If removing a question raises alpha noticeably, that question may be confusing or measuring something else — consider rewording it before the main data collection.