A 20-minute consumer survey mailed to 500 adults aged 2534 included a $5 Starbucks gift certificate. The

Question:

A 20-minute consumer survey mailed to 500 adults aged 2534 included a $5 Starbucks gift certificate. The same survey was mailed to 500 adults aged 2534 without the gift certificate. There were 65 responses from the first group and 45 from the second group. Form a 95 per- cent confidence interval for the difference of proportions. Does it include zero?