Forty-nine items are randomly selected from a population of 500 items

Compute basic descriptive statistics.

1. Forty-nine items are randomly selected from a population of 500 items.  The sample mean is 40 and the sample standard deviation 9.  Develop a 99% confidence interval for the population mean.

 

2. As a condition of employment, Fashion Industries applicants must pass a drug test. Of the last 220 applicants, 14 failed the test.  Develop a 99% confidence interval for the proportion of applicants who fail the test.  Would it be reasonable to conclude that 10% of the applicants fail the test?  Explain.

 

3. Given the following hypotheses:

 

A random sample of 12 observations is selected from a normal population.  The sample mean was 407 and the sample standard deviation 6.  Use the .01 significance level:

a. State the decision rule.

b. Compute the value of the test statistic.

c. What is your decision regarding the null hypothesis?

4. The management of White Industries is considering a new method of assembling its golf cart.  The present method requires 42.3 minutes, on the average, to assemble a cart.  The mean assembly time for a random sample of 24 carts, using the new method, was 40.6 minutes, and the standard deviation of the sample was 2.7 minutes.  Using the .10 level of significance, can we conclude that the assembly time using the new method is faster?

 

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