A political analyst were curious if younger adults were becoming more
conservative. He decided to see if the mean age of registered
Republicans was lower than that of registered Democrats. He selected
an SRS of 120 registered Republicans from a list of registered
Republicans and determined the mean age to be years with a standard
deviation years. He also selected an independent SRS of 300 registered
Democrats from a list of registered Democrats and determined the mean
age to be years with a standard deviation years. Let and represent the
mean ages of the populations of all registered Republicans and
Democrats, respectively. Suppose that the distributions of age in the
populations of age in the populations of registered Republicans and
of registered Democrats have the same standard deviation. Assuming
two sample t procedures are safe to use. A 90% confidence interval for
μ1 – μ2 is:
.
a. –1 ± 1.66 years.
b. 1 ± 2.76 years.
c. –1 ± 1.74 years.
d. –1 ± 1.98 years.