Population vs sample: population in statistical study is the entire group of individuals about which we want info. Sample part of population from which we actually collect information. Use sample to draw conclusion about entire population. Sampling design how to choose a sample from population. Sample survey: first step: say what population we want to describe, second step: say what we want to measure. Give definitions of our variable: last step: sampling design. Are biased b/c people w/ strong opinions most likely respond: a poll. Interviewer makes the choice; personal choices produce bias. Sample chosen by chance rules out both favouritism by sampler and self-selection by respondents: gives everybody a chance. Your sample contains the individuals whose label you find in the table: read two digits along, and ignore groups that are not used as labels (ex. 69 from sample labelled to 28), and ignore any repeated.