A researcher wished to compare the average amount of time spent in extracurricular activities by high school students in a suburban school district with that of high schoolers in a school district of a large city. The researcher obtained an SRS of 60 high school students in a large suburban school district and found the mean time spent in extracurricular activities per week to be x1 = 6 hours, with a standard deviation s1 = 3 hours. The researcher also obtained an independent SRS of 40 high school students in a large city school district and found the mean time spent in extracurricular activities per week to be x2 = 4 hours, with a standard deviation s2 = 2 hours. Let u1 and u2 represent the mean amount of time spent in extracurricular activities per week by the populations of all high school students in the suburban and city school districts, respectively. Assume the two-sample t-procedures are safe to use. With a level of 5%, test the hypothesis that the amount of time spent on extracurricular activities is no different in the two groups.
For the problem above, a 95% confidence interval for u1-u2 is (use the conservative value for the degrees of freedom)
a. 2 +- 0.5 hours.
b. 2 +- 0.84 hours.
c. 2 +- 1.01 hours.
d. 2 +- 1.34 hours