cba: Calculate Cronbach's Alpha reliability-coefficient from...

In betafunctions: Functions for Working with Two- And Four-Parameter Beta Probability Distributions and Psychometric Analysis of Classifications

Calculate Cronbach's Alpha reliability-coefficient from supplied variables.

Description

Calculates Cronbach's Alpha reliability coefficient of the sum-score.

Usage

cba(x)

Arguments

x	A data-frame or matrix of numerical values where rows represent respondents, and columns represent items.

Value

Cronbach's Alpha for the sum-score of supplied variables.

Note

Missing values are treated by passing na.rm = TRUE to the var function call.

Be aware that this function does not issue a warning if there are negative correlations between variables in the supplied data-set.

References

Cronbach, L.J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika 16, 297–334. doi: 10.1007/BF02310555

Examples

# Generate some fictional data. Say 100 students take a 50-item long test
# where all items are equally difficult.
set.seed(1234)
p.success <- rBeta.4P(100, 0.25, 0.75, 5, 3)
for (i in 1:50) {
  if (i == 1) {
    rawdata <- matrix(nrow = 100, ncol = 50)
  }
  rawdata[, i] <- rbinom(100, 1, p.success)
}
# To calculate Cronbach's Alpha for this test:
cba(rawdata)

betafunctions documentation built on May 29, 2024, 1:13 a.m.