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Table 1 Distribution of Demographic and Socioeconomic Variables Among Included, Excluded and Potential Controls in a Case-Control Study of Campylobacter Enteritis, England 2005-6

From: Effect of reminders on mitigating participation bias in a case-control study

  Group 1 2 3 4 5   
   Included controls Excluded controls Active refusers Incorrect addresses Passive refusers All %
Sex Female 54.0% 58.1% 50.7% 33.6% 43.1% 7,111 48.0%
  Male 46.0% 41.9% 49.3% 66.4% 56.9% 7,703 52.0%
  Total § 3,983 1,283 2,200 749 6,599 14,814  
Age group 18-24 8.9% 6.8% 7.2% 21.8% 16.9% 1,728 11.9%
  25-34 17.9% 14.7% 11.5% 24.4% 23.4% 2,628 18.1%
  35-44 19.6% 18.8% 14.8% 21.7% 22.6% 2,992 20.6%
  45-54 19.6% 24.7% 14.0% 12.7% 15.6% 2,506 17.2%
  55-64 14.3% 17.1% 15.1% 8.7% 10.1% 2,009 13.8%
  65+ 19.6% 17.8% 37.4% 10.8% 11.3% 2,673 18.4%
  Total 3,983 1,181 2,144 743 6,485 14,536  
IMD quintile 1 (most deprived) 16.5% 15.4% 19.3% 26.4% 27.3% 3,267 22.2%
  2 16.2% 16.4% 19.7% 20.2% 19.6% 2,727 18.5%
  3 19.9% 19.3% 18.4% 19.2% 18.7% 2,808 19.0%
  4 21.5% 22.2% 20.0% 15.5% 17.5% 2,837 19.2%
  5 25.8% 26.7% 22.6% 18.7% 16.9% 3,106 21.1%
  Total 3,912 1,283 2,200 749 6,601 14,745  
  1. § Sex was not known for 66 individuals
  2. Age was not known for 344 individuals
  3. IMD quintile was missing for 135 individuals