Merge pull request splitrb#50 from elliotcm/master

A refactor of the confidence helper
unamashana · Apr 24, 2012 · 7a539b5 · 7a539b5
2 parents e2c7074 + af5bd61
commit 7a539b5
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Showing 2 changed files with 21 additions and 24 deletions.
diff --git a/lib/split/dashboard/helpers.rb b/lib/split/dashboard/helpers.rb
@@ -19,30 +19,19 @@ def round(number, precision = 2)
     def confidence_level(z_score)
       return z_score if z_score.is_a? String
 
-      z = round(z_score.to_s.to_f, 3)
-      if z > 0.0
-        if z < 1.96
-          'no confidence'
-        elsif z < 2.57
-          '95% confidence'
-        elsif z < 3.29
-          '99% confidence'
-        else
-          '99.9% confidence'
-        end
-      elsif z < 0.0
-        if z > -1.96
-          'no confidence'
-        elsif z > -2.57
-          '95% confidence'
-        elsif z > -3.29
-          '99% confidence'
-        else
-          '99.9% confidence'
-        end
+      z = round(z_score.to_s.to_f, 3).abs
+
+      if z == 0.0
+        'No Change'
+      elsif z < 1.96
+        'no confidence'
+      elsif z < 2.57
+        '95% confidence'
+      elsif z < 3.29
+        '99% confidence'
       else
-        "No Change"
+        '99.9% confidence'
       end
     end
   end
-end
+end
diff --git a/spec/dashboard_helpers_spec.rb b/spec/dashboard_helpers_spec.rb
@@ -8,5 +8,13 @@
     it 'should handle very small numbers' do
       confidence_level(Complex(2e-18, -0.03)).should eql('No Change')
     end
+
+    it "should consider a z-score of 1.96 < z < 2.57 as 95% confident" do
+      confidence_level(2.12).should eql('95% confidence')
+    end
+
+    it "should consider a z-score of -1.96 > z > -2.57 as 95% confident" do
+      confidence_level(-2.12).should eql('95% confidence')
+    end
   end
-end
+end