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Table 4 Illustration of the effect of collapsing exposure categories

From: Spurious interaction as a result of categorization

X1=1 X1=2
\( {\overset{\sim }{X}}_2 \) Diseased Not diseased Total RR \( {\overset{\sim }{X}}_2 \) Diseased Not diseased Total RR
1 50 650 700 1.00 1 25 275 300 1.00
2 50 250 300 2.33 2 125 575 700 2.14
  1. The table gives the observed situation after collapsing