Refer to Exercise 8.1 and obtain a \(95 \%\) confidence interval for the difference in mean tensile strength.

Data From Exercise 8.1 

Data From Exercise 2.58

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8.1 Refer to Exercise 2.58, where n = 30 specimens of 2 x 4 lumber have x = 1,908.8 and s = 327.1 psi. A second sample of size n = 40 specimens of larger dimension, 2 x 6, lumber yielded y = 2,114.3 and s2 = 472.3. Test, with = 0.05, the null hy- pothesis of equality of mean tensile strengths versus the one-sided alternative that the mean tensile strength for the second population is greater than that of the first.