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The use of seat belts by drivers was investigated in an EL Paso, Texas study. Drivers were monitored at convenience stores picked at random. They were asked to answer questions after getting out of their cars, including questions about seat belt use. Although$75\%$ of respondents indicated they always wear seat belts, only $61.5$ percent were doing so when they pulled into the store parking lots.

A simple random sample (SRS) of size $n$ is made up of $n$ people chosen from the population with an equal chance of being the sample that is actually chosen.

A selection bias or a non-response bias could occur. Most persons who do not wear seat belts are unlikely to tell you the truth. As a result, the results will be skewed, and the sample will not be representative of the full population. As a result, it is unlikely that all seat belt polls will point in the same way.