Question: Mail survey response rate. Can you increase the response rate for a mail survey by contacting the respondents before they receive the survey? A study designed to address this question compared three groups of subjects. The first group received a preliminary letter about the survey, the second group was phoned, and the third received no preliminary contact. A positive response was defined as returning the survey within two weeks. Here are the counts:

Intervention

Response Letter Phone call None

Yes 171 146 118

No 220 68 455

Total 391 214 573

(a) For each intervention find the proportion of positive responses.

(b) Translate the question of interest into appropriate null and alternative hypotheses for this problem.

(c) Give the test statistic, degrees of freedom, and the P – value for the significance test. What do you conclude?