Assess the unidimensionality of a set of items from alpha coefficient.
Usage
alpha_curve(data)
Arguments
data
a Dataframe that holds the test response data
Value
The number of items used to calculate the coefficient.The maximum value of the alpha coefficient calculated at each step.The item removed at each step.Tue Cronbach-Mesbah curve plot.
Details
Constructs the curve by iteration:
1. Compute alpha using all items.
2. Remove one item from the scale. The removed item is the one which leaves the scale
with its maximum alpha value. If we remove a bad item, the alpha coefficient will
increase. Whereas if we remove a good item, the alpha must decrease.
3. Repeat until only two items remain.
This function was extracted from CMC_1.0 package.
References
Cameletti, M. & Caviezel, V. (2010). Checking the unidimensionality in R
using the Cronbach-Mesbah curve.
Mesbah, M. (2010). Statistical quality of life. In "Method and Applications of Statistics in the
Life and Health Sciences", N. BalakrishnanEd., Wiley, pp. 839-864.