A random sample of 35 undergraduate students who completed two years of college were asked to take a basic mathematics test. The

mean and standard deviation of their scores were 75.1 and 12.8, respectively. In a random sample of 50 students who only completed high school, the mean and standard deviation of the test scores were 72.1 and 14.6, respectively. Estimate with 90% confidence the difference in mean scores between the two groups of students. Assume the populations are approximately normal and σ1^2 ≠ σ2^2