# Cronbachs Alpha calculator

*Load data set*

On DATAtab you can calculate Cronbach's alpha online simply select the variables for which you want to calculate the Cronbach's alpha.

The results of the calculated Cronbach's alpha are then clearly displayed.

The following table from George and Mallery (2003) can be used to interpret Cronbach's Alpha

Cronbachs Alpha | Interpretation |
---|---|

> .9 | Excellent |

> .8 | Good |

> .7 | Acceptable |

> .6 | Questionable |

> .5 | Poor |

< .5 | Unacceptable |

Values much larger than 0.9 are again considered critical, as this indicates that some features are too similar and thus the same thing comes out.

## Calculate discriminatory power online

In the case of high reliability, the items of a scale should be able to distinguish between persons with a low characteristic value and a high characteristic value. This is given if the items are selective.

## Calculating discriminatory power

The discriminatory power is a measure of the correlation and is calculated with the help of the correlation. The discriminatory power can have values between 0 and 1. For an item, the discriminatory power is calculated from the correlation of this item with the value of the scale to which the item belongs. However, it is important that the respective item is not included in the calculation of the scale. The higher the discriminatory power, the better this item represents the entire scale to which it belongs.

## Calculate Cronbach's alpha

The following equation is used to calculate Cronbach's alpha:

The Cronbach's alpha thus increases when the number of items is increased and when the inter-item correlation increases. The Cronbach's alpha, on the other hand, becomes smaller when the average inter-item correlation becomes smaller.