The breaking strength of yarn supplied by two manufacturers is being investigated. We know from experience with the manufacturers' processes that crl = 5 and u2 = 4 psi. A random sample of 20 test specimens from each manufacturer results in :•1 = 88 and ,f2 = 91 psi, respectively.
(a) Using a 90% CI on the difference in mean breaking strength, comment on whether or not there is evidence to support the claim that manufacturer 2 produces yarn with higher mean breaking strength.
(b) Using a 98% CI on the difference in mean breaking strength, comment on whether or not there is evidence to support the claim that manufacturer 2 produces yarn with higher mean breaking strength.
(c) Comment on why the results from parts (a) and (b) are different or the same. Which would you choose to make your decision and why?