Exam 9: Estimation and Confidence Intervals

A nationwide survey of college students was conducted and found that students spend two hours Per class hour studying. A professor at your school wants to determine whether the time students Spend at your school is significantly different from the two hours. A random sample of fifteen Statistics students is carried out and the findings indicate an average of 1.75 hours with a standard Deviation of 0.24 hours.

Given: null hypothesis is that the population mean is 16.9 against the alternative hypothesis that the Population mean is not equal to 16.9. A random sample of 16 items results in a sample mean of 17.1 And the sample standard deviation is 2.4. It can be assumed that the population is normally Distributed. Determine the observed "t" value.

The Jamestown Steel Company manufactures and assembles desks and other office equipment at Several plants. The weekly production of the Model A325 desk follows a normal probability Distribution, with a mean of 200 and a standard deviation of 16. Recently, due to market expansion, New production methods have been introduced and new employees hired. The vice president of Manufacturing would like to investigate whether there has been a change in the weekly production Of the Model A325 desk. Is the mean number of desks produced different from 200? The mean Number of desks produced last year (50 weeks, because the plant was shut down two weeks for Vacation) is 203.5. Test using the .01 significance level. i. The alternate hypothesis is μ ≠ 200. ii. The calculated value of z is 2.55. iii. The decision rule is: if the computed value of the test statistic is not between -2.58 and 2.58, Reject the null hypothesis.

i. To prevent bias, the level of significance is selected before setting up the decision rule and Sampling the population. ii. The fifth and final step in testing a hypothesis is taking a sample and, based on the decision rule, Deciding if the null hypothesis should be rejected. iii. When the null hypothesis is not rejected, the conclusion is that our sample data does not allow Us to reject the null hypothesis.

Given: null hypothesis is that the population mean is 16.9 against the alternative hypothesis that the Population mean is not equal to 16.9. A random sample of 25 items results in a sample mean of 17.8 And the sample standard deviation is 2.4. It can be assumed that the population is normally Distributed. Determine the observed "t" value.

If the alternate hypothesis states that μ does not equal 4,000, what is the rejection region for the Hypothesis test?

The sample size and the population proportion are respectively represented by what symbols?

Based on the Nielsen ratings, the local CBS affiliate claims its 11:00 PM newscast reaches 41% of the Viewing audience in the area. In a survey of 100 viewers, 36% indicated that they watch the late Evening news on this local CBS station. What is the alternate hypothesis?

Based on the Nielsen ratings, the local CBS affiliate claims its 11:00 PM newscast reaches 41% of the Viewing audience in the area. In a survey of 100 viewers, 36% indicated that they watch the late Evening news on this local CBS station. What is the z-statistic?

One of the major U.S. tire makers wishes to review its warranty for their rainmaker tire. The warranty Is for 40,000 miles. The tire company believes that the tire actually lasts more than 40,000 miles With a standard deviation of 15,000 miles. A sample 49 tires revealed that the mean number of Miles is 45,000 miles. Test the hypothesis with a 0.05 significance level.

The printout below refers to the weekly closing stock prices for Air Canada on 20 randomly Selected weeks in 2000. Using a 5% level of significance, can you say that the average Air Canada stock price was less than $18)00?

It is claimed that in a bushel of peaches less than ten percent are defective. A sample of 400 Peaches is examined and 50 are found to be defective. What is the null hypothesis?

What is the critical value for a one-tailed hypothesis test in which a null hypothesis is tested at the 5% level of significance based on a sample size of 25 and an unknown population standard Deviation?

A manufacturer claims that less than 1% of all his products do not meet the minimum government Standards. A survey of 500 products revealed ten did not meet the standard. If the level of significance is 2%, what is the critical value?

What is a Type II error?

The dean of a business school claims that the average starting salary of its graduates is more than $50,000. It is known that the population standard deviation is $10,000. Sample data on the starting Salaries of 20 randomly selected recent graduates yielded a mean of $55,000. What is the value of The sample test statistic?

Which of the following is NOT one of the five steps in the hypothesis testing procedure?

A machine is set to fill the small size packages of Smarties candies with 56 candies per bag. A Sample revealed: 3 bags of 56, 2 bags of 57, 1 bag of 55, and 2 bags of 58. How many degrees of Freedom are there?

A restaurant that bills its house account monthly is concerned that the average monthly bill exceeds $200 per account. A random sample of twelve accounts is selected, resulting in a sample mean of $220 and a standard deviation of $12. The t-test is to be conducted at the 5% level of significance.

What is the critical value for t in a one-tailed hypothesis test in which a null hypothesis is tested at The 5% level of significance based on a sample size of 15?