An article in the Sacramento Bee was headlined, "Drop found in risky behavior among teens over last decade" (June 7, 2000, p. A6; reprinted from the Los Angeles Times). The article reported that "the findings show that for the general population [not a specific ethnic group], the share of teens abstaining from all 10 risky behaviors jumped from 20 percent to 25 percent [from the beginning to the end of the 1990s]."
The article did not say who was measured but was obviously based on samples taken at each end of the decade.
What additional information would you need to know to determine whether or not this drop represents a real drop in the percentage of the population of teens abstaining? Explain.