Table 4

Number of questions answered
Model 1*
Mean (S.E) p-value
Incentive group Control group Incentive vs control group
a) Pre-reminder 6.72 (0.033) 6.60 (0.038) 0.015
b) Total 6.70 (0.030) 6.56 (0.032) 0.001
Model 2**
Mean (S.E) p-value
Incentive group Control group Incentive vs control group
a) Pre-reminder 6.71 (0.032) 6.60 (0.036) 0.029
b) Total 6.70 (0.029) 6.57 (0.031) 0.002

GLM Univariate Analysis.

* Model 1. Number of questions answered as dependent variable and respondents in the incentive group or controll group (1,0) as fixed factor.

** Model 2. The same as model 1 but with gender, age and education as covariates. Age and education are significant in both the pre-reminder and total models.

Olsen et al.

Olsen et al. BMC Medical Research Methodology 2012 12:52   doi:10.1186/1471-2288-12-52

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