Statistics is an important tool that helps us make inferences about a population when we are only able to consider a sample. Hypothesis testing can be used to explore whether there has been a change in a particular population parameter or whether a parameter is actually different than what had previously been assumed.

Testing the Waters

In 2014, residents of Flint, Michigan began to suspect their water was contaminated with lead after the city switched its water source. The Michigan Department of Environmental Quality (DEQ) conducted an investigation and found Flint’s water to be compliant with federal water safety regulations, which require that under [latex]10\%[/latex] of homes yield water samples that have lead levels of [latex]15[/latex] parts per billion (ppb) or above. However, the residents of the city were not convinced, and they took their own sample of residences as part of the Flint Water Study (FWS).^[1]