Coefficient Alpha or Cronbach's Alpha

 Coefficient Alpha (also called "alpha") is a statistical value indicating the degree of internal consistency of items in a multiple-item scale like survey items or Likert-type scales.

Internal consistency is one measure of reliability for scores from scales, measures, and survey items.

The alpha statistic was developed by Lee Cronbach in 1951 thus it is also called Cronbach's alpha. In research reports, you may just see the Greek lower case letter alpha, α.

The procedure to calculate alpha can be found in SPSS under Analyze > Scale > Reliability.

You can also calculate alpha using Excel or Google Sheets.

Scroll down to see how to calculate alpha and get a report using Microsoft Copilot.

For research purposes, scales with alpha levels equal to or above alpha = .70 are acceptable. The best scales have values of alpha = .9 or higher.

The alpha method works best to evaluate unidimensional measures. If there are two or more dimensions in a set of items, the alpha value will be lower so, when alpha values are low, consider which item or items do not support the primary dimension.

Cite this Post

Sutton, G.W. (2021, April 26). Coefficient Alpha or Cronbach’s Alpha. Retrieved from https://statistics.suttong.com/2021/04/coefficient-alpha-or-cronbachs-alpha.html

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Calculating Cronbach’s Alpha

Organize data in a spreadsheet like Excel© or Google Sheets

Create a prompt to enter into Copilot / Chat GPT

Upload or paste the data with the prompt.

You can upload a file using drag and drop into the chat.

Example

I analyzed the 8-item Hope Scale for 15 participants from an old study.

Each row is a participant. Each column contains the scores for the 8 items.

Here is my prompt:

“Please calculate Cronbach’s alpha for this dataset, provide a table of inter-item correlations, and generate an APA-style reliability report.”

This is a picture from my Excel Spread Sheet.

This is what the paste looked like in Copilot.

ID hope1 hope2 hope3 hope4 hope5 hope6 hope7 hope8 1 6 8 7 7 6 8 7 7 2 7 6 8 6 7 6 7 5 3 7 4 6 6 6 7 6 6 4 7 7 7 7 7 8 8 6 5 8 8 8 8 7 7 6 6 6 8 3 5 8 5 8 6 5 7 4 8 7 7 7 8 7 7 8 8 8 8 8 8 8 8 8 9 5 7 7 7 6 6 6 7 10 5 6 7 7 6 3 4 3 11 7 8 8 7 8 8 8 7 12 7 7 6 6 3 6 6 5 13 8 7 7 7 7 3 8 7 14 6 6 6 5 6 5 5 4 15 5 8 5 7 8 8 8 8

Here's the Basic Response

Thanks for sharing the full dataset, Geoffrey! Based on your 15 participants and 8 Hope Scale items, the Cronbach’s alpha was calculated as:

🧪 Cronbach’s Alpha = 0.8375

📊 Interpretation:

• This value suggests strong internal consistency among the 8 items.

• In psychometric terms:

o ≥ 0.9: Excellent

o 0.8–0.9: Good

o 0.7–0.8: Acceptable

o < 0.7: Questionable or poor

So your Hope Scale items are reliably measuring a cohesive construct — likely dispositional hope or agency pathways, depending on your theoretical framework.

The item-total correlations table

Here are the item-total correlations for your 8-item Hope Scale, Geoffrey — a great way to assess how well each item aligns with the overall construct:

Item Item-Total Correlation

Hope1 0.514

Hope2 0.637

Hope3 0.648

Hope4 0.648

Hope5 0.603

Hope6 0.556

Hope7 0.715

Hope8 0.699

Interpretation:

• Hope7 and Hope8 show the strongest correlations, suggesting they’re highly representative of the overall scale.

• Hope1 has the weakest correlation (0.514), which may indicate it’s slightly less aligned with the latent construct of hope — though still within acceptable range.

• All items exceed the commonly accepted threshold of 0.3–0.4, supporting good internal consistency.

Here is the basic report in APA style.

   APA-Style Reliability Report: Hope Scale

Method

Participants (N = 15) completed the 8-item Hope Scale, designed to assess dispositional hope through agency and pathways thinking. Each item was rated on an 8-point Likert scale, with higher scores indicating greater levels of hope.

Results

Internal consistency reliability was evaluated using Cronbach’s alpha. The scale demonstrated good reliability, with α = .84, indicating strong internal consistency among the items.

Item-total correlations were calculated to assess the contribution of each item to the overall scale. All items exceeded the recommended threshold of .30, suggesting adequate homogeneity. The item-total correlations ranged from .51 (Hope1) to .72 (Hope7), with the majority falling above .60.

Item Item-Total Correlation

Hope1 .51

Hope2 .64

Hope3 .65

Hope4 .65

Hope5 .60

Hope6 .56

Hope7 .72

Hope8 .70

Discussion

The Hope Scale exhibited strong internal reliability in this sample, supporting its use as a measure of dispositional hope. The item-total correlations suggest that all items contribute meaningfully to the construct, with Hope7 and Hope8 showing particularly high alignment. These findings are consistent with prior validations of the scale and reinforce its psychometric robustness.

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Page updated 22 August 2025