From 002b87397d749ed9dfb2dc68a63685475c10d60a Mon Sep 17 00:00:00 2001 From: Jeremy Evans Date: Wed, 22 Aug 2012 14:17:46 -0700 Subject: [PATCH] Remove bad check in cronbach_alpha calculation There is no reason to return nil if a single vector has a 0 variance. For example, let's say you are giving a test, and every single taker gets the easiest question correct. The variance for that question vector is 0, but Cronbach's alpha can still be calculated correctly for the entire dataset. --- lib/statsample/reliability.rb | 1 - 1 file changed, 1 deletion(-) diff --git a/lib/statsample/reliability.rb b/lib/statsample/reliability.rb index e5fb50c..ba5deae 100644 --- a/lib/statsample/reliability.rb +++ b/lib/statsample/reliability.rb @@ -5,7 +5,6 @@ class << self # only uses tuples without missing data def cronbach_alpha(ods) ds=ods.dup_only_valid - return nil if ds.vectors.any? {|k,v| v.variance==0} n_items=ds.fields.size return nil if n_items<=1 s2_items=ds.vectors.inject(0) {|ac,v|