Gallup reported in March 2012 that 73% of American investors say that a politically divided federal government is hurting the U.S. investment climate “a lot.” Is there any evidence that the percentage has changed significantly from the 74% reported in September 2011? (These results are based on questions asked of a random sample of 1022 U.S. adults having investable assets of $10,000 or more.)

a) Find the z-score of the observed proportion.

b) Is there evidence that the proportion has decreased?

c) Explain your conclusion.