A Study Conducted by the National Center for Health Statistics

A study conducted by the National Center for Health Statistics as part of the Center for Disease Control and Prevention (CDC) found that, as of 2015-2016, 39.6% of Americans over the age of 20 fit the medical definition of being obese (BMI of 30 or higher) . A city known for its plentiful outdoor opportunities believes that number is lower among its residents. A representative sample of 80 city residents is collected and the BMI calculated for each (based on reported height and weight) . The variable of interest is whether the resident fit the medical definition of obese. The study found 22 people in the sample fit the medical definition of obese.
-Identify which of the following is the null hypothesis.

A) The sample proportion of 80 city residents that fit the medical definition of obese is equal to 0.396.
B) The long-run proportion of city residents that fit the medical definition of obese is equal to 0.396.
C) The long-run proportion of all Americans over the age of 20 that fit the medical definition of obese is equal to 0.396.
D) The sample proportion of 80 city residents that fit the medical definition of obese is equal to 0.275.