cocron.two.coefficients() R function from [cocron]

Statistical comparisons of two alpha coefficients

Performs a test of significance for the difference between two alpha coefficients (Cronbach, 1951). The function expects alpha coefficients as input.


cocron.two.coefficients(alpha, n, dep = FALSE, r = NULL, los = 0.05,
  alternative = "two.sided")

Arguments

alpha: A numeric vector containing the two alpha coefficients.
n: A numeric vector containing the number of individuals who provided the data for the test for which alpha coefficients were determined.
dep: A logical indicating whether alpha coefficients are based on dependent groups of individuals (default is FALSE).
r: A single number specifying the correlation between the scores the alpha coefficients are based on. Only required if the alpha coefficients are computed for dependent groups of individuals (dep = TRUE).
los: A number indicating the level of significance (default is .05).
alternative: A character string specifying the alternative hypothesis; must be "two.sided" (default), "greater", or "less" (or just the initial letter).

Returns

Returns an object of the class "cocron.two.coefficients" with the following slots: - alpha: Input parameter

n: Input parameter
dep: Input parameter
r: Input parameter
los: Input parameter
alternative: Input parameter
statistic: The value of the test statistic
distribution: The distribution of the test statistic
df: The degrees of freedom of the distribution of the test statistic
p.value: The p-value of the test

Details

For comparing two dependent or independent alpha coefficients (Cronbach, 1951), the methods described in Charter and Feldt (1996) are available, which were originally introduced in Feldt (1969) and Feldt (1980).

Examples


# independent alpha coefficients
cocron.two.coefficients(alpha=c(.78,.71), n=c(41,151), dep=FALSE)

# dependent alpha coefficients
cocron.two.coefficients(alpha=c(.82,.89), n=27,dep=TRUE, r=.74)

References

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

Charter, R. A., & Feldt, L. S. (1996). Testing the equality of two alpha coefficients. Perceptual and Motor Skills, 82, 763-768.

Feldt, L. S. (1969). A test of the hypothesis that Cronbach's alpha or Kuder-Richardson coefficient twenty is the same for two tests. Psychomelrika, 34, 363-373.

Feldt, L. S. (1980). A test of the hypothesis that Cronbach's alpha reliability coefficient is the same for two tests administered to the same sample. Psychometrika, 45, 99-105.

cocron.two.coefficients function