Use the data in file spanish.dat Let domain 1 consist of students who are planning a trip to a Spanish-speaking country in the next year and domain 2 consist of the students who are not planning such a trip. We are interested in whether the mean vocabulary score (y) differs in the two domains. The population domain mean in domain 1 is U1 and the population domain mean in domain 2 is U2. Using regression, estimate U1 − U2 and give a 95% CI. Is there evidence that the domain means differ?