Pick up the newspaper or turn on the television and no doubt you will read about or hear the result of one of the many polls taken daily of the public’s beliefs, attitudes, values, and opinions. Claims such as “Sixty five percent of Americans approve of the way the President is handling the economy,” “48% of people age 40 or over have not started saving for retirement,” “54% of high school kids report that they could obtain marijuana if they wanted it” are not difficult to find in the media. If you look closely at such polls, you will notice that typically they are based on the responses of only a small fraction of the people in the population that the pollsters are making statements about. How it is possible that a researcher can make a statement about an entire population by asking questions of a small, indeed only a tiny fraction of the population of interest?