6. A recent article describes a method of analyzing digital music files to determine the key in which the music is written. In a sample of 307 pop music selections, the key was identified correctly in 245 of them. In a sample of 347 new-age selections, the key was identified correctly in 304 of them. Can you conclude, at the 5% significance level, that the method is less accurate for pop songs than for new-age songs? 7. A stress analysis was conducted on random samples of epoxy-bonded joints from two species of wood. A random sample of 20 joints from species A had a mean shear stress of 1250 psi and a standard deviation of 350 psi, and a random sample of 45 joints from species B had a mean shear stress of 1400 psi and a standard deviation of 250 psi. Find and interpret a 99% confidence interval for the difference in mean shear stress between the two species. Assume the population variances are equivalent. 8. A crayon manufacturer is comparing the effects of two kinds of yellow dye on the brittleness of crayons. Dye B is more expensive than dye A, but it is thought that it might produce a stronger crayon. Four crayons are tested with each kind of dye, and the impact strength (in joules) is measured for each. The results are as follows: Dye A 1.0 2.0 1.2 3.0 Dye B 3.0 3.2 2.6 3.4 At the 5% significance level, can it be determined that dye B should be used? Assume population variances are equivalent.