Skip to main content

Table 6 Notation for a general two-by-two table

From: Bias magnification in ecologic studies: a methodological investigation

  exposed unexposed sum
cases p i m i 1 q i m i 0 p i m i 1+q i m i 0
noncases (1-p i )m i 1 (1-q i )m i 0 (1-p i )m i 1+ (1-q i )m i 0
total m i 1 m i 0 n i = m i 1+m i 0
risks p i q i  
RD p i -q i   
X i    m i 1 /n i
Y i    (p i m i 1+q i m i 0)/n i
  1. Let p i and q i be the risks of the exposed and unexposed in group i. Let m i 1and m i 0be the numbers of exposed and unexposed in group i. RD = risk difference; X i and Y i are the average exposure and average risk in group i; n i = size of group i.