Question

Reducing scrap of 4-foot planks of hardwood is an important factor in reducing cost at a wood-flooring manufacturing company Accordingly, engineers at Lumberworks are investigating a potential new cutting method involving lateral sawing that may reduce the scrap rate. To examine its viability, samples of 500 and 400 planks, respectively, were examined under the old and new methods Sixty-five of the 500 planks were scrapped under the old method, whereas 30 of the 400 planks were scrapped under the new method (You may find it useful to reference the appropriate table: z table or t table) a. Construct the 95% confidence interval for the difference between the population scrap rates between the old and new methods respectively (Negative values should be indicated by a minus sign. Round intermediate calculations to at least 4 decimal places and final answers to 2 decimal places.) Confidence interval is % to b. Select the null and alternative hypotheses to test for differences in the population scrap rates between the old and new cutting methods, respectively Mg: P1 - P2 0; Ma: P P2 Mg: P-P2s 0; MAt P-P2 Hgi P1 P2 z 0 HA P P2 c. Using the part a results, can we conclude at the 5% significance level that the scrap rate of the new method is different than the old method? We are different between the old and new methods HO. At the 5% significance level, we conclude the proportions

Answer 1

a)

confidence interval =1.58 % to 9.42 %

b)

c)

we reject Ho...........we have sufficent evidence to conclude.,,,,,,