# Yule: Yule coefficient of correlation In IRTpp: Estimating IRT Parameters using the IRT Methodology

## Description

The Yule coefficient of is a correlation coefficient applied to dichotomous data. Given a two x two table of counts | a | b | R1 | | c | d | R1 | |—|—|—-| |C1 | C2| n | or a vector c(a,b,c,d) of frequencies.

## Usage

 `1` ```Yule(x, Y = FALSE) ```

## Arguments

 `x` a 1 x 4 vector or a matrix 2 x 2 of frequencies. `Y` if Y is true return Yule's Y coefficient of colligation.

## Details

The coefficient of Yule is calculated from (ad - bc)/(ad + bc). This is the number of pairs in agreement (ad) - the number in disagreement (bc) over the total number of paired observations.

## Value

the value of the Yule Q coefficient.

## References

Yule, G.U. (1912). On the methods of measuring the association between two attributes. Journal of the Royal Statistical Society, 75, 579-652.

Warrens, Matthijs (2008), On Association Coefficients for 2x2 Tables and Properties That Do Not Depend on the Marginal Distributions. Psychometrika, 73, 777-789.

## Examples

 ```1 2``` ```#x <- c(12,8,16,9) #Yule(x) ```

IRTpp documentation built on May 29, 2017, 9:58 a.m.