In order to investigate the relationship between mean job tenure in years among workers who have a bachelors degree or higher and those who do not, random samples of each type of worker were taken, with the following results. The following data was recorded: n x a
Bachelor's degree or higher 155 5.2 1.3
No degree 210 5 1.5

Required:
a. Construct the 99% confidence interval for the difference in the population means based on these data.
b. Test, at the 1% level of significance, the claim that mean job tenure among those with higher education is greater than among those without, against the default that there is no difference in the means.
c. Compute the observed significance of the test.