In a public opinion survey, 70 out of a sample of 100 high-income voters and 55 out of a sample of 80 low-income voters supported the introduction of a new national security tax. a/ Estimate, with 95% confidence level, the true proportion of high-income people who will vote for the introduction of the tax.
b/ Can we conclude at the 5% level of significance that the proportion favoring the new security tax differs between high-income and low-income voters?