Armstrong, J.S. (1975). Monetary incentives in mail surveys. Public Opinion Quarterly, 39, 111-116. Find information (the survey, an article, etc.) that describes a particular monetary incentive that was used in a real survey.
What do you think about it? Do you think that it impacts the accuracy of the responses? Or, do you think it is necessary? Why or why not? This post can include your personal opinions.