Alpha {bruceR}

Reliability analysis (Cronbach's \alpha and McDonald's \omega).

Description

An extension of psych::alpha() and psych::omega(), reporting (1) scale statistics (Cronbach's \alpha and McDonald's \omega) and (2) item statistics (item-rest correlation [i.e., corrected item-total correlation] and Cronbach's \alpha if item deleted).

Three options to specify variables:

1. var + items: common and unique parts of variable names (suggested).

2. vars: a character vector of variable names (suggested).

3. varrange: starting and stopping positions of variables (NOT suggested).

Usage

Alpha(data, var, items, vars = NULL, varrange = NULL, rev = NULL, digits = 3)

Arguments

data

Data frame.

var

[Option 1] Common part across variables: e.g., "RSES", "XX.{i}.pre" (if var string has any placeholder in braces {...}, then items will be pasted into the braces, see examples)

items

[Option 1] Unique part across variables: e.g., 1:10, c("a", "b", "c")

vars

[Option 2] Character vector specifying variables: e.g., c("X1", "X2", "X3", "X4", "X5")

varrange

[Option 3] Character string specifying positions ("start:stop") of variables: e.g., "A1:E5"

rev

[Optional] Variables that need to be reversed. It can be (1) a character vector specifying the reverse-scoring variables (recommended), or (2) a numeric vector specifying the item number of reverse-scoring variables (not recommended).

digits

Number of decimal places of output. Defaults to 3.

Value

A list of results obtained from psych::alpha() and psych::omega().

See Also

MEAN, EFA, CFA

Examples

# ?psych::bfi
data = psych::bfi
Alpha(data, "E", 1:5)   # "E1" & "E2" should be reversed
Alpha(data, "E", 1:5, rev=1:2)            # correct
Alpha(data, "E", 1:5, rev=cc("E1, E2"))   # also correct
Alpha(data, vars=cc("E1, E2, E3, E4, E5"), rev=cc("E1, E2"))
Alpha(data, varrange="E1:E5", rev=cc("E1, E2"))

# using dplyr::select()
data %>% select(E1, E2, E3, E4, E5) %>%
  Alpha(vars=names(.), rev=cc("E1, E2"))