equating.fun: Equating scales between different application contexts.

In Nwosu/JAN_17_RM_weights: Weighted Rasch Modeling and Extensions using Conditional Maximum Likelihood

Description

This function calibrates the measure derived by a scale applied in one context (for example, country) to the metric of a reference scale, or standard (for example, the scale applied in another country, or in the same country but through a different survey, or to any other standard). The main output is the prevalence rate in the country of interest calculated at specified thresholds along the latent trait.

Usage

equating.fun(rr1, st=NULL, tol = .35, spec.com1 = 1:8, spec.com2=1:8, 
thres = NULL, maxuniq=3, write.file=F, plot=F, iterative=T, excl.prior1,
excl.prior2)

Arguments

rr1	The Rasch model fitted with the RM.w function for the country of interest.
st	Item severity parameter estimates for the reference country or the standard. The number of items for the standard can differ from the number of items of the country of interest.
tol	Tolerance expressed in the metric of the standard, above which items are considered unique (i.e. not contributing to the common metric between the two countries). Default is 0.35.
spec.com1	A priori numbered set of comparable items for the country of iterest to the standard. Items must be specified in the same order as they are used for the comparison.
spec.com2	A priori set of comparable items for the standard. The length of spec.com1 and spec.com2 should be the same.
thres	Thresholds (along the latent trait) corresponding to which the comparable prevalence rates of the phenomenon of interest is calculated. Default is set to the 5-th and the 8-th item of the standard specified in st.
maxuniq	A priori maximum number of unique items allowed.
write.file	Logical argument. If TRUE, a csv file with the relevant information about the equating process is created in the working directory.
plot	Logical argument. If TRUE, a pdf file with a plot of the equated item severities is produced in the working directory. Default is FALSE.
iterative	Logical argument. If TRUE, an iterative process to identify which item is unique is performed. Otherwise, unique items are specified in the arguments excl.prior1 and excl.prior2 and are taken as fixed. Default is TRUE.
excl.prior1	Numbered set of fixed unique items for the country of interest. It needs to be specified only if iterative = FALSE.
excl.prior2	Numbered set of fixed unique items for the standard. It needs to be specified only if iterative = FALSE.

Value

scale	Scale parameter to be applied to the metric of the country of interest to be considered equivalent to the standard.
shift	Shift parameter to be applied to the metric of the country of interest to be considered equivalent to the reference country. The standardized item parameters for the country of interest will be: b.country.st=shift+scale*b.country where b.country are estimated item severities for the country of interest.
common	Vector of logical, TRUE when the item in the country of interest is common.
prevs	Prevalence rates for the country of interest, calculated on the metric of the standard.
prevs.rs	Prevalence rates for the country of interest, calculated on the metric of the standard, calculated at each raw score threshold.
cor.comm.items	Correlation between common items.
adj.thres	Adjusted (equated) thresholds on the country metric.

Author(s)

Sara Viviani [e-mail]

See Also

prob.assign

Examples

## Not run: 
data(data.FAO_country1)
XX.country1 = data.FAO_country1[,1:8]
wt.country1 = data.FAO_country1$wt
rr1=RM.w(XX.country1, wt.country1)
data(data.FAO_country2)
XX.country2 = data.FAO_country2[,1:8]
wt.country2 = data.FAO_country2$wt
rr2=RM.w(XX.country2, wt.country2)
# Iterative equating
ee1=equating.fun(rr1, st=rr2$b, thres=c(-0.28, 1.85), spec.com1=c(1:8),spec.com2=c(1:8))
# Not iterative equating: fixing WORRIED unique
ee2=equating.fun(rr1, st=rr2$b, thres=c(-0.28, 1.85),spec.com1=c(1:8),
spec.com2=c(1:8), tol = .4,iterative=F,excl.prior1=1,excl.prior2=1)
# Prevalence rates
ee1$prevs
ee2$prevs

## End(Not run)

Nwosu/JAN_17_RM_weights documentation built on May 7, 2019, 8:20 p.m.