Question

1. A textile mill wants to test the strength of the fiber of a certain batch of cotton. The Pressley Strength Index measures fiber strength in thousands of pounds of pressure required to break the equivalent of one square inch of fiber. The expected strength level for the population of cotton used by the company is a population mean strength of 90 pounds. The sample of 26 pieces of fiber is drawn. The sample has a mean strength of 85.50 pounds of pressure with a sample standard deviation of 15.25 pounds. The company is concerned that this batch of cotton does not measure up to the company’s standard for quality fabric strength.

1. Set up the null and alternative hypotheses. Will it be one-tailed lower, One-tailed upper or two-tailed test?

2. Determine the Critical Rejection value. Will it be a Z-test or a T-test? Set up the acceptable alpha level = .05.

3. Calculate the test value based upon the sample data and expected population mean.

4. What is you’re the acceptable variance of conclusion? What advice would you tell the company?

Answer 1