1. a) What is the population of interest to the researcher (how many individuals)?
The researcher is interested in examining voting behavior of individuals. So his population of interest would be anyone who is eligible to vote. As there are 7000 people in the town eligible to vote that means his population of interest is 7000.
1. b) What is the sample of interest to the researcher (how many individuals)?
The sample of interest to the researcher would be the sample of people he managed to interview, in this case 70% of the 5000 people contacted agreed to be interviewed. This means his sample of interest is 3500.