Table 6.

Syntax for computing ICCs in SPSS and R.

SPSS Syntax
RELIABILITY
/VARIABLES=Emp_Rater1 Emp_Rater2 Emp_Rater3
/SCALE(‘ALL VARIABLES’) ALL
/MODEL=ALPHA
/ICC=MODEL(RANDOM) TYPE(CONSISTENCY) CIN=95 TESTVAL=0.
R Syntax
library(irr)	#Load the irr package (must already be installed)
hist(myRatings[,1]))	#Examine histogram for rater 1 for violations of normality
hist(myRatings[,2]))	#Examine histogram for rater 2
print(icc(myRatings, model=“twoway”, type=“consistency”, unit=“average”))
	#Specify the ICC model, type, and unit as appropriate.
	#Use help(icc) for keywords

Note: R syntax assumes that data are in a matrix or data frame called “myRatings.” In SPSS, model may be MIXED, RANDOM, or ONEWAY, type may be CONSISTENCY or ABSOLUTE. Single- and average-measures units will be included in SPSS output. In R, model may be twoway or oneway, type may be consistency or absolute, and unit may be average or single.