Cronbach's Alpha
Computes Cronbach's alpha, the most used measure of internal consistency of a questionnaire or scale. It answers: do the items that should measure the same thing actually agree with each other? The formula combines the number of items with the ratio between the sum of each item's variance and the total-score variance. Values above 0.7 usually indicate acceptable reliability. It's indispensable in psychometrics and instrument validation. Enter the item variances and the total-score variance.
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Cronbach's Alpha
Computes Cronbach's alpha, the most used measure of internal consistency of a questionnaire or scale. It answers: do the items that should measure the same thing actually agree with each other? The formula combines the number of items with the ratio between the sum of each item's variance and the total-score variance. Values above 0.7 usually indicate acceptable reliability. It's indispensable in psychometrics and instrument validation. Enter the item variances and the total-score variance.
Do the questionnaire items agree with each other?
When you build a scale with several questions to measure a single thing, self-esteem, satisfaction, pain, a question arises: do these questions really pull in the same direction, or does each measure something different? Cronbach's alpha is the classic answer, the most used measure of internal consistency in psychometrics since 1951.
The idea is to compare each item's variance with the total-score variance. If the items agree, their sum has much greater variance than the sum of the isolated parts, and alpha approaches 1. By convention, values above 0.7 indicate acceptable reliability, above 0.8 good, and below 0.5 signal that the scale is probably measuring too many things at once.
Enter the variances of each item and the total-score variance of the scale. The tool returns alpha. Mind the interpretation: an alpha that's too high (above 0.95) can indicate redundant items, and alpha grows artificially just by adding items, so it doesn't replace a validity analysis of the instrument.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.