What is the Kronbach coefficient?

Cronbach's α (Cronbach's α) is a statistic, which refers to the average of semi-reliability coefficients obtained by all possible item division methods of the scale, and is the most commonly used reliability measurement method. It was first named by American educator Lee Kronbach in 195 1 year. Where k is the number of samples, σ2X is the variance of the total samples, and σ2Yi is the variance of the currently observed samples.

Cronbach alpha

In general, Cronbach α coefficient is between 0 and 1. If the x coefficient does not exceed 0.6, it is generally considered that the reliability of internal consistency is insufficient; When it reaches 0.7-0.8, it shows that the scale has considerable reliability, and when it reaches 0.8-0.9, it shows that the reliability of the scale is very good.

An important feature of Cronbach α coefficients is that their values will increase with the increase of scale items. Therefore, Cronbach α coefficient may be artificially and inappropriately increased because the scale contains redundant measurement items.

There is also a coefficient that can be used at the same time as the Cronbach α coefficient. Coefficient can help to evaluate whether the calculation of average value conceals some irrelevant measurement items in the process of calculating Cronbach α coefficient.

Different researchers have different views on the limit value of reliability coefficient. Some scholars believe that Cronbach α coefficient should be at least 0.8 in basic research, at least 0.7 in exploratory research and at least 0.6 in practical research.

definition

The definition of standardized Cronbach α coefficient, if a quantity table has n questions and the average correlation coefficient between the questions is r, then the standardized α coefficient of this table is, α=nr/[(n- 1)r+ 1].