I am new on this forum and this is rather a question on the same theme than a reply. Does it make sense to test that 2 random effects are significantly different? I.e. to be more specific: assume that you have subjects clustered within a institution and you have subjects characteristic (x1) and institution characteristic (x2). There is an interest in comparing the highest performing institution with the lowest after adjusting for the mentioned characteristics. My outcome is continuous therefore proc mixed as in: proc mixed; class institution; model y=x1 x2; random institution/s; estimate "Institution 1 vs 2" | institution 1 -1; estimate "institution 1 vs 3" |institution 1 0 -1; run; The estimates above seem to be comparing the random effects for institution and therefore the institutions but not sure if this makes sense. Any opinion? Thanks, Ruxandra
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