A random sample of 100 high-school dropouts in Pittsburgh aged 17 to 19 revealed that 20% of them were unemployed.
a. Place a 95% confidence interval on the percentage of all similar people in that area who are unemployed.
b. The average unemployment rate for the entire work force in Pittsburgh is 7.0%. Is the unemployment rate among high-school dropouts significantly higher than for the entire work force? Justify your answer.