Gallup reported in 2012 that 53% of American investors are likely to say the price of energy (including gas and oil) is hurting the U.S. investment climate “a lot,” according to a Wells Fargo/Gallup Investor and Retirement Optimism Index survey. The survey results are based on questions asked February 3-12, 2012, of a random sample of 1022 U.S. adults having investable assets of $10,000 or more. The percentage reported to this same question in September 2011 was 62%.
a) Is the percentage in 2012 different from that in 2011? Test the appropriate hypothesis. Check conditions. Does the test provide evidence that the percentage has changed from 2011?
b) Find a 95% confidence interval for the sample Economic Confidence Index.