The effect of cash lottery on response rates to an online health survey among members of the Canadian Association of Retired Persons: a randomized experiment.
Doerfling P, Kopec JA, Liang MH, Esdaile JM. The effect of cash lottery on response rates to an online health survey among members of the Canadian Association of Retired Persons: a randomized experiment. Can J Public Health. 2010 May-Jun; 101(3):251-4.