Researchers measured skulls from different time periods in an attempt to determine whether interbreeding of cultures occurred. Results are given below (based on data from Ancient Races of the Thebaid, by Thomson and Randall-Maciver, Oxford University Press). Use a 0.01 significance level to test the claim that the mean maximal skull breadth in 4000 b.c. is less than the mean in a.d. 150.

Assume that the two samples are independent simple random samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. Do the following:
a. Test the given claim using the P-value method or critical value method.
b. Construct a confidence interval suitable for testing the given claim.

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4000 в.с. (Maximal Skull Breadth): n 30,--131.37 mm, s 5.13 mm A.D. 150 (Maximal Skull Breadth) 30,x 136.17 mm, 5.35 mm