An environmental survey contained a question asking what respondents thought was the major cause of air pollution in this country, giving the choices “automobiles,” “factories,” and “incinerators.” Two versions of the test, A and B, were used. Let pA and pB be the respective proportions of people using forms A and B who select “factories.” If 170 out of 460 people who used version A chose “factories” and 141 out of 440 people who used version B chose “factories,”
(a) Find a 95% confidence interval for pA − pB.
(b) Do the versions seem to be consistent concerning this answer? Why or why not?