In studying his campaign plans, Mr. Singleton wishes to estimate the difference between men's and women's views regarding his appeal as a candidate. He asks his campaign manager to take two random independent samples and find the 90% confidence interval for the difference. A random sample of 516

male voters and 592 female voters was taken. 135 men and 201 women favored Mr. Singleton as a candidate. Find the critical value that should be used in constructing the confidence interval.