Exam 9: Hypothesis Tests

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.

The academic planner of a university thinks that at least 35% of the entire student body attends summer school.The correct set of hypotheses to test his belief is

Exhibit 9-9 The sales of a grocery store had an average of $8,000 per day.The store introduced several advertising campaigns in order to increase sales.To determine whether or not the advertising campaigns have been effective in increasing sales,a sample of 64 days of sales was selected.It was found that the average was $8,300 per day.From past information,it is known that the standard deviation of the population is $1,200. -Refer to Exhibit 9-9.The value of the test statistic is

If a hypothesis is rejected at 95% confidence,it

For a one-tailed test (lower tail),a sample size of 10 at 90% confidence,t =

In hypothesis testing,the tentative assumption about the population parameter is

Consider the following hypothesis test: H_o: $\mu$ 38 H_a: $\mu$ > 38 You are given the following information obtained from a random sample of six observations.Assume the population has a normal distribution. a.Compute the mean of the sample b.Determine the standard deviation of the sample. c.Determine the standard error of the mean. d.Compute the value of the test statistic. e.At 95% confidence using the p-value approach,test the above hypotheses.

"D" size batteries produced by MNM Corporation have had a life expectancy of 87 hours.Because of an improved production process,it is believed that there has been an increase in the life expectancy of its "D" size batteries.A sample of 36 batteries showed an average life of 88.5 hours.Assume from past information that it is known that the standard deviation of the population is 9 hours. a.Formulate the hypotheses for this problem. b.Compute the test statistic. c.What is the p-value associated with the sample results? What is your conclusion based on the p-value? Let $\alpha$ = .05.

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

A weatherman stated that the average temperature during July in Chattanooga is 80 degrees or less.A sample of 32 Julys is taken.The correct set of hypotheses is

A Type II error is committed when

For a one-tailed test (upper tail),a sample size of 18 at 95% confidence,t =

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.

The Bureau of Labor Statistics reported that the average yearly income of dentists in the year 2009 was $110,000.A sample of 81 dentists,which was taken in 2010,showed an average yearly income of $120,000.Assume the standard deviation of the population of dentists in 2010 is $36,000. a.We want to test to determine if there has been a significant increase in the average yearly income of dentists.Provide the null and the alternative hypotheses. b.Compute the test statistic. c.Determine the p-value;and at 95% confidence,test the hypotheses.

For a two-tailed test at 98.4% confidence,Z =

Exhibit 9-6 A random sample of 16 students selected from the student body of a large university had an average age of 25 years and a standard deviation of 2 years.We want to determine if the average age of all the students at the university is significantly more than 24.Assume the distribution of the population of ages is normal. -Refer to Exhibit 9-6.The p-value is between

An automobile manufacturer stated that it will be willing to mass produce electric-powered cars if more than 30% of potential buyers indicate they will purchase the newly designed electric cars.In a sample of 500 potential buyers,160 indicated that they would buy such a product. a.State the hypotheses for this problem b.Compute the standard error of. c.Compute the test statistic. d.At 95% confidence,what is your conclusion? Should the manufacturer produce the new electric powered car?

When the p-value is used for hypothesis testing,the null hypothesis is rejected if

For a one-tailed test (lower tail)at 89.8% confidence,Z =

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.The test statistic is