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Table 2 Distribution of Demographic and Socioeconomic Variables Among Included Controls by Mailing Wave 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

1A

1B

1C

 
  

First mailing

First reminder

Second reminder

Total§

Sex

Female

56.0%

49.5%

51.9%

53.3%

χ 2 p = 0.004

Male

44.0%

50.5%

48.1%

45.2%

 

Total

2507

703

717

3927

Age group

18-24

5.4%

6.0%

10.3%

6.3%

χ 2 p < 0.001

25-34

12.6%

13.1%

14.8%

12.9%

 

35-44

19.0%

20.5%

24.7%

20.0%

 

45-54

20.0%

21.2%

20.8%

20.1%

 

55-64

20.0%

19.2%

15.1%

18.7%

 

65+

23.1%

20.1%

14.4%

20.7%

 

Total

2507

703

717

3927

Age at leaving full-time education

< 16 yrs

28.3%

30.9%

26.1%

28.3%

χ 2 p = 0.007

16 yrs

29.4%

29.3%

34.6%

30.4%

 

17 yrs

9.0%

9.5%

8.8%

9.0%

 

18 yrs

11.5%

9.1%

10.3%

10.9%

 

19 yrs

20.5%

19.2%

17.1%

19.6%

 

Still in education

1.3%

1.9%

3.1%

1.8%

 

Total †

2463

692

706

3861

IMD quintile

1 (most deprived)

15.2%

18.4%

19.0%

16.5%

χ 2 p = 0.056

2

16.0%

14.8%

18.6%

16.2%

 

3

20.3%

18.8%

19.0%

19.8%

 

4

22.5%

21.2%

19.0%

21.6%

 

5

26.0%

26.8%

24.4%

25.9%

 

Total ‡

2483

697

710

3890

  1. § 56 individuals could not be assigned to any group due to missing date information
  2. † Age at leaving full-time education was missing for 66 individuals
  3. ‡ IMD quintile was missing for 71 individuals