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

Table 3 **Results of ancillary strategies to motivate enrolment AHS-2 among black adventists: proportional increments (PI)* due to the interventions**

Sub-study	Beta coefficients (SE)	p⁺	E (PI_I)	E (PI_c)	E (PI_I)-E (PI_c)
A. Association with Baseline promotion
Black art alone compared to $10^§	0.049 (0.156)	0.754	0.463	0.441	0.022
Black art plus $10 compared to $10^§	0.512 (0.237)	0.033	0.737	0.441	0.296
B. Early post-baseline (3 months)
Telephone follow-up	1.043 (0.337)	0.004	0.098	0.035	0.063
C. Late post-baseline (9–36 months)
Student recruiters	1.002 (0.353)	0.008	0.041	0.015	0.026
Local recruiters	1.988 (0.639)	0.007	0.033	0.005	0.028
Operation 30,000	0.152 (0.120)	0.207	0.035	0.030	0.005
Tournament of healing	1.345 (0.312)	0.0001	0.054	0.014	0.040
Lake Union $20	0.558 (0.145)	0.0002	0.032	0.018	0.014
	Alpha coefficient (SE)		E (PI_I)	95% CI
Enroll another $2	-2.861 (0.198)		0.036	(0.025, 0.052)
Enroll another $10	-3.168 (0.228)		0.027	(0.017, 0.041)

*Increment expressed as proportion of the goal; PI = (returns during stipulated period)/Goal. PI_c is PI during the control period and PI_I is PI during the intervention period.
⁺p tests the null hypothesis that the beta coefficient related to PI_I/PI_c,, equals zero, and similarly tests that PI_I = PI_c.
^§Approximate mean values used for covariates in the statistical model (reference #9).

ISSN: 1471-2288