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# Hypothesis Testing Problems: Value and Traditional Approaches

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Please help with these questions. I need to be able to understand how to do them. Please write out all steps from beginning to end , formulas etc. (need answers too so I can double check myself) please do not use excel, I need to see what I am trying to learn. Please see attached.

Chapter 6 questions

1. A medical school claims that more than 28% of its students plan to go into general practice.

a. It is found that among a random sample of 130 of the school's students, 42 of them plan to go into general practice. Does this sample evidence support the school's claim? Use the p-value approach and &#61537; = 0.05 to make your decision.

b. Suppose a second sample is collected a year after the first with the results indicating 57 out of 135 plan to go into general practice. Does this sample evidence support the school's claim? Use the p-value approach and &#61537; = 0.05 to make your decision.

2. The health of employees is monitored by periodically weighing them. A sample of 54 employees has a mean weight of 183.9 lbs. Assuming that &#61555; is known to be 121.2 lb. Use a 0.10 level to test the claim that the population mean weight of all such employees is less than 200 lb.

3. A manufacturer makes ball bearings that are supposed to have a mean weight of 30 g. A retailer suspects that the mean weight is not 30 g and wants to verify that the product is meeting specifications. The mean weight for a random sample of 16 ball bearings is 29.5 g with a standard deviation of 4.1 g. At the 0.05 significance level, test the claim that the mean is not 30 g. You may assume the weights are normally distributed.

4. In tests of a computer component, it is found that the mean time between failures is 520 hours. A modification is made which is supposed to increase the time between failures. Tests on a random sample of 10 modified components resulted in the following times (in hours) between failures.

518 548 561 523 536
499 538 557 528 563

a. Find x-bar and s for this data set.

b. At the 5% significance level, test the claim that for the modified components, the mean time between failures is greater than 520 hours? You may assume the times between failures are normally distributed. Use the traditional method to make your decision.

5. A cereal company claims that the mean weight of the cereal in its packets is at least 14 oz. The weights (in ounces) of the cereal in a random sample of 8 of its cereal packets are listed below.
14.6 13.8 14.1 13.7 14.0 14.4 13.6 14.2

At the 0.01 significance level, does the sample support the company's claim that the mean weight is at least 14 ounces? You may assume the weight of cereal packets is normally distributed.

6. Various temperature measurements are recorded at different times for a particular city. The mean of 21°C is obtained for 32 temperatures on 32 different days. Assuming that &#963; = 1.5°C, test the claim that the population mean is actually less than 22°C. Use a 0.05 significance level.

#### Solution Summary

Step by step method for testing the hypothesis under 5 step approach is discussed here. Both traditional and p value method are employed here.

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## Testing of hypothesis under traditional and p value approach.

9.54 Faced with rising fax costs, a firm issued a guideline that transmissions of 10 pages or more should be sent by 2-day mail instead. Exceptions are allowed, but they want the average to be 10 or below. The firm examined 35 randomly chosen fax transmissions during the next year, yielding a sample mean of 14.44 with a standard deviation of 4.45 pages. (a) At the .01 level of significance, is the true mean greater than 10? (b) Use Excel to find the right-tail p-value.

9.56 A coin was flipped 60 times and came up heads 38 times. (a) At the .10 level of significance, is the coin biased toward heads? Show your decision rule and calculations. (b) Calculate a p-value and interpret it.

9.62 The Web-based company Oh Baby! Gifts has a goal of processing 95 percent of its orders on the same day they are received. If 485 out of the next 500 orders are processed on the same day, would this prove that they are exceeding their goal, using &#945; = .025? (See story.news.yahoo.com accessed June 25, 2004.)

9.64 An auditor reviewed 25 oral surgery insurance claims from a particular surgical office, determining that the mean out-of-pocket patient billing above the reimbursed amount was \$275.66 with a standard deviation of \$78.11. (a) At the 5 percent level of significance, does this sample prove a violation of the guideline that the average significance, does this sample prove a violation of the guideline that the average patient should pay no more than \$250 out-of-pocket? State your hypotheses and decision rule. (b) Is this a close decision?

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