In an NBC News/Wall Street Journal poll of 1,000 American adults conducted on August 5–9 , 2 0 1 0 , 44% of respondents approved of the job that Barack Obama was doing in handling the economy.

a. Compute a 90% confidence interval of the proportion of Americans who approved of Barack Obama's handling of the economy.

b. What is the resulting margin of error?

c. Compute the margin of error associated with a 99%

confidence level. P-69