View source: R/item_intercor.R
item_intercor  R Documentation 
Compute various measures of internal consistencies for tests or itemscales of questionnaires.
item_intercor(x, method = c("pearson", "spearman", "kendall"))
x 
A matrix as returned by the 
method 
Correlation computation method. May be one of

This function calculates a mean interitemcorrelation, i.e. a
correlation matrix of x
will be computed (unless x
is already a matrix
as returned by the cor()
function) and the mean of the sum of all items'
correlation values is returned. Requires either a data frame or a computed
cor()
object.
"Ideally, the average interitem correlation for a set of items should be between 0.20 and 0.40, suggesting that while the items are reasonably homogeneous, they do contain sufficiently unique variance so as to not be isomorphic with each other. When values are lower than 0.20, then the items may not be representative of the same content domain. If values are higher than 0.40, the items may be only capturing a small bandwidth of the construct." (Piedmont 2014)
The mean interitemcorrelation value for x
.
Piedmont RL. 2014. Interitem Correlations. In: Michalos AC (eds) Encyclopedia of Quality of Life and WellBeing Research. Dordrecht: Springer, 33033304. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1007/9789400707535_1493")}
data(mtcars)
x < mtcars[, c("cyl", "gear", "carb", "hp")]
item_intercor(x)
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