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Table 2 Details of control selection for each sub-study

From: Recruiting and motivating black subjects to complete a lengthy survey in a large cohort study: an exploration of different strategies

Sub study

Type of control

Number of controls/Intervention units

Timing of control period compared to intervention

A. Associated with baseline promotion

 

Black Art Alone compared to $10

Other churches*

24/19

Concurrent

 

Black Art + $10 compared to $10

 

24/62

Concurrent

B. Early post-baseline

 

Telephone follow-up

Other churches (randomized)

13/27

Concurrent

C. Mid post-baseline

 

Operation 30,000

Self (152 churches)

N/A

71 churches before and 81 after intervention period§

 

Student recruiters

Other matched churches

9/36

Concurrent

 

Local Recruiters

Other matched churches

12/10

Concurrent

 

Tournament of Healing

Other matched churches

22/38

Concurrent

D. Late post-baseline

 

Lake Union $20

Self (80 churches)

N/A

All controls are an average of periods before and after intervention

 

Enroll Another $2 bill

None

0/500

N/A

 

Enroll Another $10

None

0/500

N/A

  1. *Adjusted also for church size in the statistical model.
  2. These studies are individual subject, rather than church-based.
  3. §Likelihood weighted to restore balance.