# Question

A consumer organization tested two paper shredders, the Piranha and the Crocodile, designed for home use. Each of 10 randomly selected volunteers shredded 100 sheets of paper with the Piranha, and then another sample of 10 randomly selected volunteers each shredded 100 sheets with the Crocodile. The Piranha took an average of 203 seconds to shred 100 sheets with a standard deviation of 6 seconds. The Crocodile took an average of 187 seconds to shred 100 sheets with a standard deviation of 5 seconds. Assume that the shredding times for both machines are normally distributed with equal but unknown standard deviations.

a. Construct a 99% confidence interval for the difference between the two population means.

b. Using a 1% significance level, can you conclude that the mean time taken by the Piranha to shred 100 sheets is higher than that for the Crocodile?

c. What would your decision be in part b if the probability of making a Type I error were zero? Explain.

a. Construct a 99% confidence interval for the difference between the two population means.

b. Using a 1% significance level, can you conclude that the mean time taken by the Piranha to shred 100 sheets is higher than that for the Crocodile?

c. What would your decision be in part b if the probability of making a Type I error were zero? Explain.

## Answer to relevant Questions

Quadro Corporation has two supermarket stores in a city. The company’s quality control department wanted to check if the customers are equally satisfied with the service provided at these two stores. A sample of 380 ...Refer to Exercise 10.34. Test at a 1% significance level if the two population means are different. n1 = 48 1 = .863 s1 = .176 n2 = 46 2 = .796 s1 = .068 Refer to Exercise 10.28. Now assume that the two populations are normally distributed with unequal and unknown population standard deviations. In Exercise 28 a. Make a 90% confidence interval for the difference between the ...Refer to the information given in Exercise 10.3. Test at a 5% significance level if the two population means are different. n1 = 18 1 = 7.82 σ1 = 2.35 n2 = 15 2 = 5.99 σ1 = 3.17 What is the shape of the sampling distribution of p̂1 – p̂2 for two large samples? What are the mean and standard deviation of this sampling distribution?Post your question

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