Cronbach Alpha Calculator

Common questions

What is Cronbach’s alpha and what does it measure?

Cronbach’s alpha, or coefficient alpha, summarizes the internal consistency of a summed score from multiple items in a particular sample. It uses how the item variances compare with the variance of their total score. It is a descriptive statistic, not a test of validity or proof that all items measure one dimension. The symbol is the Greek letter α (alpha). A rough English pronunciation is “KRON-bahk AL-fuh.”

How do I prepare a CSV item matrix?

Put one observation on each data row and one item in each column. Paste comma-separated values or choose a local UTF-8 CSV, state whether the first row contains column names, and read the columns. Select 2 to 100 numeric items and leave identifiers unselected. Up to 10,000 data rows are supported. Quoted commas and escaped quotes are accepted; malformed rows are reported instead of partially imported.

How is raw Cronbach alpha calculated?

For k selected items, α = k/(k - 1) × (1 - Σs²item/s²total), where Σs²item is the sum of item sample variances and s²total is the sample variance of each respondent’s summed score. Every sample variance uses n - 1. Three identical varying columns containing 1, 2 and 3 give raw alpha 1: each item variance is 1, their sum is 3, and total-score variance is 9, so (3/2) × (1 - 3/9) = 1. Constant total scores make raw alpha undefined.

How does standardized alpha differ?

Standardized alpha uses the item correlation matrix, equivalent to giving every item unit sample variance before forming the score. Raw alpha uses the original covariance scale. Different item variances can make the results differ. A constant item makes its correlations and standardized alpha undefined, while raw alpha may still be defined.

How do reverse coding and missing observations work?

Select Reverse beside each item to reverse code and enter its declared minimum and maximum. The transformed value is minimum plus maximum minus the original value: on a 1 to 5 scale, 1 becomes 5, 3 stays 3 and 5 becomes 1. Blank, NA and N/A selected cells are missing. The calculation requires explicit consent before removing their entire rows. It never imputes values; malformed selected numbers must be corrected even on a row with another missing item.

What do corrected item-total correlation and alpha if deleted mean?

Corrected item-total correlation compares an item with the sum of the other selected items. Alpha if deleted is raw alpha for the remaining items, using the same complete rows as the full analysis. It is undefined when fewer than two items remain or the remaining total has zero variance. These are descriptive diagnostics and do not recommend deleting an item.

Can alpha be negative or undefined?

Yes. Negative estimates remain negative rather than being clipped to zero. For paired rows (1, 4), (2, 2), (3, 1), raw alpha is -18. Rows (1, 3), (2, 2), (3, 1) have constant total scores, so raw alpha is undefined. Undefined diagnostics show the specific variance or item-count reason. Extreme numeric scales that exceed representable covariance precision require rescaling.

What can I copy or export?

After calculating, copy a report with both alpha results, item diagnostics, reverse coding and every excluded row. The diagnostics CSV also includes the complete covariance and correlation matrices, sample means and variances. Displayed numbers use 8 significant digits; CSV numeric fields retain their unrounded floating-point values. Imported labels receive spreadsheet formula protection. No individual response rows are included in these exports.

Is my questionnaire data uploaded or saved?

No. CSV parsing and analysis run locally in a cancellable background worker. Inputs and results are kept in memory and are not stored in browser storage or sent to analytics. A 50 MB file or 50-million-character pasted-text budget and a two-million-cell structural budget protect browser memory. If a matrix exceeds a budget, export just the needed columns or use a smaller matrix.

What is an acceptable or good Cronbach alpha value?

There is no universal passing value or minimum. A value such as 0.6 needs context about the intended score, sample, item count and measurement model. With positive total-score variance, alpha is at most 1 but can be arbitrarily negative. A higher value does not prove validity or one-dimensional measurement, and highly similar items can raise alpha without broadening what the score measures. Read the raw and standardized labels separately; this worksheet reports estimates without a pass/fail verdict.

Can I use Likert responses or multiple-choice test scores?

Use one respondent per row and one numeric item per column. Likert responses can be entered as numeric codes, with any reverse-scored items declared explicitly. For a multiple-choice test, enter each item’s scored value, such as 0 for incorrect and 1 for correct, rather than the answer letters. For binary 0/1 items, raw alpha equals KR-20 on the same complete matrix. Alpha is not inter-rater agreement, and this page does not calculate KR-21.

How can I calculate Cronbach alpha in Excel?

For three fully numeric items in B2:D4, put =SUM(B2:D2) in E2 and fill down through E4. Then use =(3/2)*(1-(VAR.S(B2:B4)+VAR.S(C2:C4)+VAR.S(D2:D4))/VAR.S(E2:E4)). This is raw alpha for those three items and three complete rows, not standardized alpha. For more items, use k/(k-1) and include every item variance; for more respondents, extend every range to the same last row. Resolve missing entries and reverse coding before forming totals, since spreadsheet sums can otherwise omit blank cells. The original example here gives 1 with this formula.

How does alpha differ from correlation or composite reliability?

A correlation coefficient describes a pair of variables; standardized alpha combines the correlations among all selected items into a score-consistency estimate. Composite reliability uses an explicitly fitted measurement model, including loadings and error variances. This worksheet computes alpha and item correlations, not composite reliability or factor analysis.

Apa itu alpha Cronbach dan rumus uji reliabilitasnya?

Alpha Cronbach mengukur konsistensi internal skor gabungan dari beberapa item dalam suatu sampel. Rumusnya α = k/(k - 1) × (1 - jumlah varians item/varians skor total). Nilai ini bukan bukti validitas dan tidak memiliki batas lulus yang universal. Masukkan respons numerik: satu responden per baris dan satu item per kolom.

Comment interpréter l’alpha de Cronbach ?

L’alpha de Cronbach décrit la cohérence interne d’un score composé de plusieurs items dans un échantillon. Il ne prouve ni la validité ni l’unidimensionnalité. Il n’existe pas de seuil universel; une valeur négative reste négative. Le calcul utilise des réponses numériques, avec une personne par ligne et un item par colonne.

Wat is de betekenis van Cronbach alpha?

Cronbachs alfa beschrijft de interne consistentie van een totaalscore met meerdere items in een steekproef. Het bewijst geen validiteit of eendimensionaliteit. Er is geen universele grenswaarde. Voer numerieke antwoorden in, met één respondent per rij en één item per kolom.

Cronbach alpha nedir?

Cronbach alfa, bir örneklemde birden fazla maddeden oluşan toplam puanın iç tutarlılığını özetler. Geçerliliği veya tek boyutluluğu kanıtlamaz; evrensel bir kabul sınırı yoktur. Sayısal yanıtları, her satırda bir katılımcı ve her sütunda bir madde olacak şekilde girin.