In 2007, a Gallup poll estimated that 45% of U.S. adults rated their financial situation as “good.” Is the proportion different for this year? Which of the following samples could be used to test the null hypothesis p = 0.45? Mark each as valid (OK to use to test the hypothesis) or not valid (should not be used to test the hypothesis).

Hint 1

100 adults randomly selected from people shopping at malls in each of 10 major U.S. cities.

Hint 2

1,000 respondents randomly selected from the large pool of people who respond to an Internet survey posted on the CNN website.

250 adults selected randomly from active U.S. telephone or cell phone numbers in each of the four geographic regions of the U.S. (Northeast, Midwest, South, and West.)