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Shrout-Fleiss reliability coefficients

Source: R/GLM_RELIABILITY.R
shrout.Rd

Computes five reliability coefficients from the Shrout and Fleiss (1979) framework using variance components extracted from a person × item × time mixed model (see extract_components). The coefficients cover between-person and within-person reliability under both fixed and random time designs, and are appropriate for longitudinal or repeated-measures measurement studies.

Usage

shrout(sperson, spersonitem, stime, spersontime, serror, m, k)

Arguments

sperson

Variance component of the person main effect.

spersonitem

Variance component of the person × item interaction.

stime

Variance component of the time main effect.

spersontime

Variance component of the person × time interaction.

serror

Variance component of residual error.

m

Number of items (reports) averaged over.

k

Number of time points averaged over.

Value

A data frame with one row per reliability coefficient containing columns measure, result, and description:

r1f

Between-person reliability of a single measure at fixed time points.

r1r

Between-person reliability of a single measure at random time points (different people, different days).

rkf

Between-person reliability of scores averaged over m items and k fixed time points.

rkr

Between-person reliability of scores averaged over k random time points.

rc

Within-person reliability of change across time points.

References

Shrout, P. E., & Fleiss, J. L. (1979). Intraclass correlations: Uses in assessing rater reliability. Psychological Bulletin, 86(2), 420–428.

Examples

design<-expand.grid(time=1:3,item=1:2,person=1:10)
design<-change_data_type(design,type="factor")
design$response<-rnorm(30,0,0.1)
model<-mixlm::lm(response~r(time)*r(person)+r(item)*r(person),data=design)
result<-extract_components(model)
vc<-result$components
shrout(sperson=vc[2,3],spersonitem=vc[5,3],stime=vc[1,3],
       spersontime=vc[4,3],serror=vc[6,3],3,3)
#>   measure result                                                                                         description
#> 1     r1f 0.4219                            Reliability (between persons) of measures taken on the same fixed k time
#> 2     r1r 0.2283                           Reliability (between persons) of measures taken on the same random k time
#> 3      rc 0.5927                                                              Reliability (within persons) of change
#> 4     rkf 0.6865        Reliability (between persons) of average measures taken over fixed m items and fixed k times
#> 5     rkr 0.4702 Reliability (between persons) of different random time with same number of points k between periods