Hello again. I posted this question a couple of weeks ago and since I have received no suggestions, I assume it's because I have not given enough information. If more information is needed, please let me know what you need and I'll do my best to provide it. Thanks, Kevin
On 08/31/2015 11:53 AM, Kevin E. Thorpe wrote:
Hello. I have a data frame with following structure.
> str(vision)
'data.frame': 268 obs. of 9 variables: $ Child : Factor w/ 67 levels "C01-05","C01-10",..: 43 43 43 43 44 44 44 44 42 42 ... $ Test : Factor w/ 4 levels "1","2","3","4": 1 2 3 4 1 2 3 4 1 2 ... $ Rater : Factor w/ 4 levels "F","L","P","S": 4 1 4 1 1 4 1 4 4 1 ... $ Binoc : int 100 100 100 100 0 0 0 0 40 0 ... $ Yield : int 100 100 100 80 100 20 50 30 100 100 ... $ Tries : int 5 5 5 6 5 10 10 10 5 5 ... $ Result : Factor w/ 5 levels "Pass","ReferBI",..: 1 1 1 1 3 2 3 2 3 3 ... $ ResultCollapsed: Factor w/ 3 levels "Pass","Refer",..: 1 1 1 1 2 2 2 2 2 2 ... $ Test1 : Factor w/ 16 levels "F:1","F:2","F:3",..: 13 2 15 4 1 14 3 16 13 2 ... In these data, each subject is rated by 2 (of 4) raters twice. The Test1 variable was created from Test and Rater with (Rater:Test)[drop=TRUE] to explicitly create the nesting. I then fit the following model.
> binoc.lmer1 <- lmer(Binoc~1+(1|Child) + (1|Rater) +
(1|Test1),data=vision)
> binoc.lmer1
Linear mixed model fit by REML ['lmerMod']
Formula: Binoc ~ 1 + (1 | Child) + (1 | Rater) + (1 | Test1)
Data: vision
REML criterion at convergence: 2592.62
Random effects:
Groups Name Std.Dev.
Child (Intercept) 29.226
Test1 (Intercept) 2.292
Rater (Intercept) 5.823
Residual 26.330
Number of obs: 264, groups: Child, 66; Test1, 16; Rater, 4
Fixed Effects:
(Intercept)
51.68
Now my questions.
1. Have I fit the right model?
2. If so, would the right estimate for the rater ICC be
Rater/(Rater + Residual)
or
(Rater + Test1)/(Rater + Test1 + Residual)
3. Would Test1/(Test1 + Residual) give an estimate of intra-rater
reliability?
Thanks for you time.
Kevin
Kevin E. Thorpe Head of Biostatistics, Applied Health Research Centre (AHRC) Li Ka Shing Knowledge Institute of St. Michael's Assistant Professor, Dalla Lana School of Public Health University of Toronto email: kevin.thorpe at utoronto.ca Tel: 416.864.5776 Fax: 416.864.3016