Question

A newspaper writer will write an article about the mean age of voters. She will estimate by selecting a sample of voters and calculating their mean age. Which method should the writer use to select the sample?randomly select 100 people who voted in the last election

select 100 people who voted in the last election and are more than 30 years old

select 100 people who voted for the most popular candidate in the last election

randomly select 100 people who read the newspaper

Answer 1

randomly select 100 people who voted in the last election

Answer 2

She should randomly select 100 people that voted in the last election.

This will avoid bias based on age, as we would see in the second choice. It will also ensure that the people who respond are actually voters, unlike the last choice; some people that read the newspaper may not be voters at all. Additionally, some candidates are more popular among certain age groups, so to avoid bias we should not select just voters that voted for the most popular candidate.