# Question: A company manufactures ball bearings that are supplied to other

A company manufactures ball bearings that are supplied to other companies. The machine that is used to manufacture these ball bearings produces them with a variance of diameters of .025 square millimeter or less. The quality control officer takes a sample of such ball bearings quite often and checks, using confidence intervals and tests of hypotheses, whether or not the variance of these bearings is within .025 square millimeters. If it is not, the machine is stopped and adjusted. A recently taken random sample of 23 ball bearings gave a variance of the diameters equal to .034 square millimeters.

a. Using a 5% significance level, can you conclude that the machine needs an adjustment? Assume that the diameters of all ball bearings have a normal distribution.

b. Construct a 95% confidence interval for the population variance.

a. Using a 5% significance level, can you conclude that the machine needs an adjustment? Assume that the diameters of all ball bearings have a normal distribution.

b. Construct a 95% confidence interval for the population variance.

## Relevant Questions

A random sample of 25 students taken from a university gave the variance of their GPAs equal to .19. a. Construct the 99% confidence intervals for the population variance and standard deviation. Assume that the GPAs of all ...A student who needs to pass an elementary statistics course wonders whether it will make a difference if she takes the course with instructor A rather than instructor B. Observing the final grades given by each instructor in ...Multiple choice questions: 1. The random variable x2 assumes only a. Positive b. Nonnegative c. Non-positive values 2. The parameter(s) of the chi-square distribution is (are) a. Degrees of freedom b. df and n c. x2 3. Which ...A large company buys thousands of light bulbs every year. The company is currently considering four brands of light bulbs to choose from. Before the company decides which light bulbs to buy, it wants to investigate if the ...Suppose that you are a reporter for a newspaper whose editor has asked you to compare the hourly wages of carpenters, plumbers, electricians, and masons in your city. Since many of these workers are not union members, the ...Post your question