Cronbach's alpha (internal-consistency reliability)

Cronbach's alpha, the standard index of a scale's internal-consistency reliability: how consistently a set of k items measures a single construct. Computed from the item variances and the total-score variance. The raw alpha and the mean inter-item correlation reproduce base R, the psych package (psych::alpha raw_alpha) and pingouin.cronbach_alpha bit-for-bit.

Usage

cronbachAlpha(x)

Arguments

x

A respondents-by-items numeric matrix or data frame (rows = respondents, columns = scale items). Rows with any missing value are dropped.

Value

A list with alpha (raw Cronbach's alpha), average_r (mean inter-item correlation), k (items) and n (respondents).

Examples

cronbachAlpha(matrix(round(runif(150, 1, 5)), ncol = 5))
#> $alpha
#> [1] 0.1695771
#> 
#> $average_r
#> [1] 0.04097421
#> 
#> $k
#> [1] 5
#> 
#> $n
#> [1] 30
#>