How Collected Data Tells The Truth Practice Test

A city health department investigates the research question: “Is the mean number of hours of sleep for adults in the city at least 7 hours?” Interviewers stood outside a downtown gym on weekday mornings and surveyed 85 adults leaving the gym; the sample mean was 7.4 hours. The department concluded that adults in the city average at least 7 hours of sleep. Which statement explains whether the conclusion is valid?

A county election office investigates the research question: “What proportion of registered voters in the county approve of the new voting center location?” The office used a random-digit dialing method that called only landline phone numbers in the county and completed interviews with 520 registered voters; 61% approved. The office concluded that about 61% of all registered voters in the county approve. Which statement explains whether the conclusion is valid?