Discuss the below:
Q: A postal researcher wanted to test the theory that a higher response rate is achieved when a postal questionnaire is sent out with a personalized covering letter (A) than when the covering letter is impersonal (B). Two random samples of 100 people were selected. When the questionnaires were dispatched, the first sample-received letter A and the second received letter B. The response rates to letter A were 70% and to letter B, 55%.
a) Do these results provide evidence in support of the theory?
b) Explain the reasoning behind the test.