Exam 9: Hypothesis Tests

The Department of Economic and Community Development (DECD) reported that in 2009 the average number of new jobs created per county was 450. The department also provided the following information regarding a sample of 5 counties in 2010. a.Compute the sample average and the standard deviation for 2010. b.We want to determine whether there has been a significant decrease in the average number of jobs created. Provide the null and the alternative hypotheses. c.Compute the test statistic. d.Compute the p-value; and at 95% confidence, test the hypotheses. Assume the population is normally distributed.

For a two-tailed test at 86.12% confidence, Z =

The power curve provides the probability of

Last year, a soft drink manufacturer had 21% of the market. In order to increase their portion of the market, the manufacturer has introduced a new flavor in their soft drinks. A sample of 400 individuals participated in the taste test and 100 indicated that they like the taste. We are interested in determining if more than 21% of the population will like the new soft drink. a.Set up the null and the alternative hypotheses. b.Determine the test statistic. c.Determine the p-value. d.At 95% confidence, test to determine if more than 21% of the population will like the new soft drink.

The average monthly rent for one-bedroom apartments in Chattanooga has been $700. Because of the downturn in the real estate market, it is believed that there has been a decrease in the average rental. The correct hypotheses to be tested are

A two-tailed test is performed at 95% confidence. The p-value is determined to be 0.09. The null hypothesis

A student believes that the average grade on the statistics final examination was 87. A sample of 36 final examinations was taken. The average grade in the sample was 83.96 with a standard deviation of 12. a.State the null and alternative hypotheses. b.Using the critical value approach, test the hypotheses at the 5% level of significance. c.Using the p-value approach, test the hypotheses at the 5% level of significance.

Exhibit 9-1 -Refer to Exhibit 9-1. If the test is done at 95% confidence, the null hypothesis should

In hypothesis testing,

The level of significance

The level of significance is the

Exhibit 9-5 A random sample of 100 people was taken. Eighty-five of the people in the sample favored Candidate A. We are interested in determining whether or not the proportion of the population in favor of Candidate A is significantly more than 80%. -Refer to Exhibit 9-5. At 95% confidence, it can be concluded that the proportion of the population in favor of candidate A

Exhibit 9-1 -Refer to Exhibit 9-1. The test statistic is

The average starting salary of students who graduated from colleges of Business in 2009 was $48,400. A sample of 100 graduates of 2010 showed an average starting salary of $50,000. Assume the standard deviation of the population is known to be $8,000. We want to determine whether or not there has been a significant increase in the starting salaries. a.State the null and alternative hypotheses to be tested. b.Compute the test statistic. c.The null hypothesis is to be tested at 95% confidence. Determine the critical value for this test. d.What do you conclude? e. Compute the p-value.

The level of significance in hypothesis testing is the probability of

Exhibit 9-4 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took the customers in the sample to check out was 3.1 minutes with a standard deviation of 0.5 minutes. We want to test to determine whether or not the mean waiting time of all customers is significantly more than 3 minutes. -Refer to Exhibit 9-4. At 95% confidence, it can be concluded that the mean of the population is

The school's newspaper reported that the proportion of students majoring in business is at least 30%. You plan on taking a sample to test the newspaper's claim. The correct set of hypotheses is

You are given the following information obtained from a random sample of 5 observations. Assume the population has a normal distribution. You want to determine whether or not the mean of the population from which this sample was taken is significantly less than 21. a.State the null and the alternative hypotheses. b.Compute the standard error of the mean. c.Determine the test statistic. d.Determine the p-value and at 90% confidence, test whether or not the mean of the population is significantly less than 21.

Choo Choo Paper Company makes various types of paper products. One of their products is a 30 mils thick paper. In order to ensure that the thickness of the paper meets the 30 mils specification, random cuts of paper are selected and the thickness of each cut is measured. A sample of 256 cuts had a mean thickness of 30.3 mils with a standard deviation of 4 mils. a.Compute the standard error of the mean. b. b.At 95% confidence using the critical value approach, test to see if the mean thickness is significantly more than 30 mils. c.Show that the p-value approach results in the same conclusion as that of part

A sample of 81 account balances of a credit company showed an average balance of $1,200 with a standard deviation of $126. a.Formulate the hypotheses that can be used to determine whether the mean of all account balances is significantly different from $1,150. b.Compute the test statistic. c.Using the p-value approach, what is your conclusion? Let $\alpha$ = .05.