In a public opinion survey, 80 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 low-income people who will vote for the introduction of the tax.
b/ Can we conclude at the 5% level of significance that the proportion of high-income voters favoring the new security tax is 10% higher than that of low-income voters?