• Write a null and alternative hypothesis for a hypothesis test.
• Decide if a sample statistic provides enough evidence to reject the null hypothesis.

The Flint Water Study (FWS) tested the water from [latex]271[/latex] homes and found contaminated water samples in [latex]20\%[/latex] of their sample.^[1]

Notice that in conducting this hypothesis test, we began by assuming the null hypothesis was true (i.e., it was already the assumption that Flint was compliant with federal regulations). The Flint Water Study (FWS) then collected evidence in support of the alternative—that Flint was not compliant. The possibilities are then that the FWS obtained enough evidence to reject the null hypothesis or that it did not obtain enough evidence to reject the null hypothesis.

The only possible conclusions of a hypothesis test are to reject the null hypothesis or to fail to reject the null hypothesis. There is never a conclusion to a hypothesis test in which one “accepts” the null hypothesis.

Based on the results of the Flint Water Study, as well as a study done by a pediatrician on the blood lead levels of children in Flint, the city switched the water supply back to the previous source, and the governor declared a state of emergency a few months later.

Read more about Flint water infrastructure:

• Lead testing results for water sampled by residents. (2015, September). Flint Water Study Updates. Retrieved from http://flintwaterstudy.org/information-for-flint-residents/results-for-citizen-testing-for-lead-300-kits/
• Barry-Jester, A. M. (2016, February 23). When will Flint’s water be safe to drink? FiveThirtyEight. https://fivethirtyeight.com/features/when-will-flints-water-be-safe-to-drink/
• https://www.epa.gov/flint
• https://en.wikipedia.org/wiki/Flint_water_crisis

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