
INTRACLASS CORRELATIONName:
CORRELATION RATIO (LET)
The intraclass correlation is the ratio of the weighted variance of the group means divided by the variance of all samples. The intraclass correlation coefficient can have values between 0 and 1. A value of 0 indicates no variance between the means of the different groups while a value of 1 indicates that the sample variance is due to the variance between groups rather than the variance within groups. So the intraclass correlation indicates the relative importance of the "between group variance" (values closer to 1) and "within group variance" (values closer to 0). The correlation ratio is the square root of the intraclass correlation coefficient.
<SUBSET/EXCEPT/FOR qualification> where <y> is the response variable; <x> is the groupid variable; <par> is a parameter where the intraclass correlation value is saved; and where the <SUBSET/EXCEPT/FOR qualification> is optional.
<SUBSET/EXCEPT/FOR qualification> where <y> is the response variable; <x> is the groupid variable; <par> is a parameter where the correlation ratio value is saved; and where the <SUBSET/EXCEPT/FOR qualification> is optional.
LET CR = CORRELATION RATIO Y X LET CR = CORRELATION RATIO Y X SUBSET X > 2
. Step 1: Create some data (from Wikipedia page on Correlation Ratio) . read x y 1 45 1 70 1 29 1 15 1 21 2 40 2 20 2 30 2 42 3 65 3 95 3 80 3 70 3 85 3 73 end of data . . Step 2: Compute the statistics . let cr = correlation ratio y x let icc = intraclass correlation y x set write decimals 4 print cr icc PARAMETERS AND CONSTANTS CR  0.8386 ICC  0.7033  
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Date created: 08/30/2019 