Questions from Engineering Statistics

Q: A random sample of 20 students yielded a mean of ¯x

A random sample of 20 students yielded a mean of ¯x = 72 and a variance of s2 = 16 for scores on a college placement test in mathematics. Assuming the scores to be normally distributed, construct a 98...

Q: Construct a 95% confidence interval for σ2 in Exercise 9.

Construct a 95% confidence interval for σ2 in Exercise 9.9 on page 283. Exercise 9.9: Regular consumption of presweetened cereals contributes to tooth decay, heart disease, and other degenerative dis...

Q: Construct a 99% confidence interval for σ2 in Exercise 9.

Construct a 99% confidence interval for σ2 in Exercise 9.11 on page 283. Exercise 9.11: A machine produces metal pieces that are cylindrical in shape. A sample of pieces is taken, and the diameters a...

Q: Construct a 99% confidence interval for σ in Exercise 9.

Construct a 99% confidence interval for σ in Exercise 9.12 on page 283. Exercise 9.12: A random sample of 10 chocolate energy bars of a certain brand has, on average, 230 calories per bar, with a sta...

Q: Construct a 90% confidence interval for σ in Exercise 9.

Construct a 90% confidence interval for σ in Exercise 9.13 on page 283. Exercise 9.13: A random sample of 12 shearing pins is taken in a study of the Rockwell hardness of the pin head. Measurements o...

Q: Construct a 98% confidence interval for σ1/σ2 in Exercise

Construct a 98% confidence interval for σ1/σ2 in Exercise 9.42 on page 295, where σ1 and σ2 are, respectively, the standard deviations for the distances traveled per liter of fuel by the Volkswagen an...

Q: Construct a 90% confidence interval for σ21/σ22 in Exercise

Construct a 90% confidence interval for σ21/σ22 in Exercise 9.43 on page 295. Were we justified in assuming that σ21 ≠ σ22 when we constructed the confidence interval for μ1 − μ2? Exercise 9.43: A ta...

Q: Construct a 90% confidence interval for σ21/σ22 in Exercise

Construct a 90% confidence interval for σ21/σ22 in Exercise 9.46 on page 295. Should we have assumed σ21 = σ22 in constructing our confidence interval for &...

Q: An efficiency expert wishes to determine the average time that it takes

An efficiency expert wishes to determine the average time that it takes to drill three holes in a certain metal clamp. How large a sample will she need to be 95% confident that her sample mean will be...

Q: Construct a 95% confidence interval for σ2A/σ2B in Exercise

Construct a 95% confidence interval for σ2A/σ2B in Exercise 9.49 on page 295. Should the equal-variance assumption be used? Exercise 9.49: Two different brands of latex paint ar...