% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/icvi.R
\name{icvi}
\alias{icvi}
\title{Item-level Content Validity Index (I-CVI)}
\usage{
icvi(ratings, relevant_threshold = 3, na.rm = FALSE)
}
\arguments{
\item{ratings}{A numeric matrix or data frame of expert ratings, where rows
represent experts and columns represent items. Values are typically on a
1-4 relevance scale. A numeric vector is also accepted, treated as a
single item.}

\item{relevant_threshold}{Integer. The minimum rating considered "relevant".
Defaults to 3 (i.e., ratings of 3 or 4 count as relevant on a 4-point
scale).}

\item{na.rm}{Logical. If \code{TRUE}, missing ratings are excluded from the
calculation. Defaults to \code{FALSE}, in which case any \code{NA} produces \code{NA}
for the affected item.}
}
\value{
A named numeric vector of I-CVI values, one per item. If \code{ratings}
is a vector, returns a single numeric value.
}
\description{
Computes the Item-level Content Validity Index (I-CVI) for one or more items
rated by a panel of experts on a relevance scale. Following Lynn (1986) and
Polit & Beck (2006), I-CVI is calculated as the proportion of experts who
rate an item as 3 (relevant) or 4 (highly relevant) on a 4-point relevance
scale.
}
\details{
Common interpretation guidelines (Polit & Beck, 2006):
\itemize{
\item I-CVI >= 0.78: excellent content validity (with 6 or more experts).
\item I-CVI 0.70-0.78: acceptable, item may need revision.
\item I-CVI < 0.70: item should be revised or eliminated.
}

With fewer than six experts, Lynn (1986) recommends a stricter cutoff of
I-CVI = 1.00 for unanimous agreement.
}
\examples{
# Five experts rating four items on a 1-4 relevance scale
ratings <- matrix(
  c(4, 4, 3, 4, 4,    # Item 1
    3, 4, 4, 4, 3,    # Item 2
    2, 3, 3, 4, 3,    # Item 3
    1, 2, 3, 2, 3),   # Item 4
  nrow = 5,
  dimnames = list(NULL, paste0("item", 1:4))
)
icvi(ratings)

# Single item supplied as a vector
icvi(c(4, 4, 3, 3, 4))

# Stricter threshold (only highest rating counts as relevant)
icvi(ratings, relevant_threshold = 4)

}
\references{
Lynn, M. R. (1986). Determination and quantification of content validity.
\emph{Nursing Research}, 35(6), 382-385.
\doi{10.1097/00006199-198611000-00017}

Polit, D. F., & Beck, C. T. (2006). The content validity index: Are you
sure you know what's being reported? Critique and recommendations.
\emph{Research in Nursing & Health}, 29(5), 489-497.
\doi{10.1002/nur.20147}
}
