Solutions for Session 1, Part D

See solutions for Problems: D1 | D2| D3

 Problem D1 One such question is "Are girls better math students than boys?" Consider this question for the population of a certain school. A representative sample would be a selection of girls across grade and ability levels and a selection of boys across grade and ability levels. An unrepresentative sample might select only one grade level or one ability level. Comparing the girls and boys in the most challenging math course at the school would be a very unrepresentative sample.

 Problem D2 It is difficult to select a simple random sample if full information about the population is not available. It would be extremely difficult to select a simple random sample of the world's ant population, for instance, since it would be impractical (if not impossible) to obtain enough information about the population to set up the random sample.

 Problem D3 A census is still considered a sample because there is no guarantee that the attempt to include everyone has been successful. For example, every 10 years, the U.S. population census misses between 1% and 3 % of the individuals in the population, and accidentally counts some people more than once. A full census for all but the smallest populations would be impossible to complete successfully.