Chapter 8, Problem 37SE

Global Warming Historically (from about 2001 to 2014), $57\%$ of Americans believed that global warming is caused by human activities. A March 2017 Gallup poll of a random sample of 1018 Americans found that 692 believed that global warming is caused by human activities.

a. What percentage of the sample believed global warming was caused by human activities?

b. Test the hypothesis that the proportion of Americans who believe global warming is caused by human activities has changed from the historical value of $57\%.$ Use a significance level of $\mathrm{0.01.}$

c. Choose the correct interpretation:

i. In 2017, the percentage of Americans who believe global warming is caused by human activities is not significantly different from $57\%.$

ii. In 2017, the percentage of Americans who believe global warming is caused by human activities has changed from the historical level of $57\%.$