Confidence intervals for Cronbach's alpha wihtout the data {Cronbach}

Confidence intervals for Cronbach's alpha wihtout the data

Description

Confidence intervals for Cronbach's alpha wihtout the data.

Usage

cronfree.ci(a, p, n, conf = 0.95, type = "kf")

Arguments

a

The Cronbach's alpha.

p

The number of items or variables.

n

The sample size of the data.

conf

The confidence level of the interval

type

The type of confidence interval to compute, "kf" or "whalen". See details for more information.

Details

This function contains some confidence intervals for Cronbach's alpha. The "kf" was described in Tsagris, Frangos and Frangos (2013) and stands for the method of Koning A. and Franses H. P. (2006). The "whalen" stands for the method of Rodriguez and Maeda (2006). The difference with the confidence intervals produced by cron.ci is that with these methods the data are not necessary.

Value

A confidence interval for the true value of alpha.

Author(s)

Michail Tsagris, Christos Frangos and Constantinos Frangos.

R implementation and documentation: Michail Tsagris [e-mail], Christos Frangos [e-mail] and Constantinos Frangos [e-mail].

References

Tsagris M., Frangos C.C. and Frangos C.C. (2013). "Confidence intervals for Cronbach's reliability coefficient". Recent Techniques in Educational Science, 14-16 May, Athens, Greece. http://www.academia.edu/download/32613010/Cronbachs_alpha.pdf

Rodriguez M. C. and Maeda Y. (2006). "Meta-analysis of coefficient alpha". Psychological methods, 11(3): 306-322.

Koning A. and Franses H. P. (2006). "Confidence intervals for Cronbach's coefficient alpha values". Technical report, Erasmus Research Institute of Management-ERIM.

Cronbach L. (1951). "Coefficient alpha and the internal structure of tests". Psychometrika, 16(3): 297-334.

See Also

cron.ci, cronbach

Examples

## silly example
x <- as.matrix( iris[1:50, 1:4] )
a <- Cronbach::cronbach(x)
Cronbach::cronfree.ci(a, 4, 150)