6. A stress analysis was conducted on random samples of epoxy-bonded (a type of glue) joints from tw

6. A stress analysis was conducted on random samples of epoxy-bonded (a type of glue) joints from two wood species. The “shear stress” (at what point the bonds broke) in psi summary for the two species is below:

Assume the calculated degrees of freedom are: = 207

(a) Create a 90% confidence interval for the true differ-ence in average shear stress for the two species.

(b) Interpret your confidence interval from (a) in terms of the problem.

(c) The conductor of the analysis wants a narrower con- fidence interval. Theoretically, what are his options?

(d) What assumptions did we need in order for this con- fidence interval to be valid?