Table 2

The effect of financial incentive on responses

ReturnedNot returned
Financial v non-financial incentive method
    Financial incentive (n=217)128 89
    No financial incentive (n=217)103114
    χ2 analysisχ2 = 5.78, 1 df, p=0.016
Individual administration methods (with/without financial incentive)
    Postal with financial incentive6141
    Postal without incentive5547
    χ2 analysisχ2 = 0.83, 1 df, p=0.47
    Telephone with financial incentive4520
    Telephone without incentive2936
    χ2 analysisχ2 = 8.03, 1 df, p=0.005
    Clinic visit with financial incentive2228
    Clinic visit without incentive1931
    χ2 analysisχ2 = 0.37, 1 df, p=0.17