A 20-minute consumer survey mailed to 500 adults aged 25–34 included a $5 Starbucks gift certificate.
The same survey was mailed to 500 adults aged 25–34 without the gift certificate. There were 65 responses from the first group and 45 from the second group. (a) Perform a two-tailed test comparing the response rates (proportions) at α = .05. (b) Form a confidence interval for the difference of proportions, without pooling the samples. Does it include zero?
Please provide how you figured out the results.