Statistical comparisons of n alpha coefficients

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Description

Performs a test of significance for the difference between n alpha coefficients (Cronbach, 1951). The function expects raw data input from which the alpha coefficients are calculated.

Usage

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cocron(data, dep = FALSE, standardized = FALSE, los = 0.05,
  conf.level = 0.95)

Arguments

data

A list holding two or more data.frames/matrices with rows and columns corresponding to individuals and items, respectively. From each data.frame/matrix an alpha coefficients is determined.

dep

A logical indicating whether the alpha coefficients are based on dependent groups of individuals

standardized

A logic indicating whether a standardized Cronbach alpha should be calculated (default is FALSE).

los

A number indicating the level of significance (default is .05).

conf.level

A number defining the level of confidence for the confidence intervals of the alpha coefficients (default is .95; see cronbach.alpha.CI). The confidence intervals serve as additional information only, they are not used for the test of significance.

Details

To compare n dependent or independent alpha coefficients (Cronbach, 1951), the methods by Feldt, Woodruff, and Salih (1987) implemented in cocron.n.coefficients are used.

Value

Returns an object of the class "cocron.n.coefficients" (see cocron.n.coefficients).

References

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

Feldt, L. S., Woodruff, D. J., & Salih, F. A. (1987). Statistical inference for coefficient alpha. Applied Psychological Measurement, 11, 93-103.

See Also

cocron.n.coefficients, cocron.two.coefficients

Examples

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data("knowledge")

# independent alpha coefficients
cocron(knowledge, dep=FALSE)

# dependent alpha coefficients
cocron(knowledge, dep=TRUE)