Decide whether the sampling method could result in a biased sample. Write yes or no, and explain your reason.

1. A west coast based lawn service is trying to figure out how much water people use on average each month to water their lawn. They send surveys to people in Phoenix, Arizona and Seattle, Washington to compile this data.

2. Asking people in a library about the number of magazines to which they subscribe to in order to describe the reading habits of a town.

Decide whether the situation is an experiment or an observational study. Give at least one reason.
3. A teacher plays music during all tests given in a one-month period and compares the class grades with a similar class that does not have music played during tests.

4. A real estate developer records the listing and selling prices of all homes in one area to determine the difference in the listing price and the selling price.