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 33 of the 400 planks were scrapped under the new method.

a. Construct the 99% confidence interval for the difference between the population scrap rates between the old and new methods, respectively.

Confidence interval is % to %.

Answer 1

Given that, n1 = 500 and x1 = 65

n2 = 400 and x2 = 33

Using TI-84 calculator we get, 99% confidence interval for the difference between the population scrap rates between the old and new methods is, ( -0.0050, 0.1000)

In percentage: (-0.5% , 10%)

=> Confidence interval is -0.5% to 10%