Researchers collected data from residents of a city with a population of 100,000 people to assess awareness of physical activity guidelines. Because of the difficulty of mailing surveys to people in the city, the researchers collected data from a convenience sample of 1,000 people (1%the people who walked past city hall on a Wednesday morning). The researchers decided to focus on determining whether three factors were associated with having good or poor awareness of physical guidelines (variable 1): age (variable 2), gender (variable 3), and years of education (variable 4). Only 61% of the respondents answered the question about years of education