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1.The Big Break Moving Company claims that a typical family moves an average of once every 5.2 yrs. In a random sample of 100 families, the average length of time between moves as yrs. With a standard deviation of 1.8 yr. Does this indicate that the average moving time is different from 5.2 yrs? (Use a 5% level of significance.)

2.A machine in the student lounge dispenses coffee. The average cup of coffee is supposed to contain 7.0 oz. Eight cups of coffee from this machine show the average content to be 7.3 oz. with a standard deviation of 0.5 oz. Do you think the machine has slipped out of adjustment and the average amount of coffee per cup is different from 7 oz.? Use a 5% level of significance.

3.Leeville has two high schools; one in the older part of town and the other in the new section of town. The school board wants to determine if student performance at the two schools is different. To make the comparison, they decided to compare composite scores on the ACT college admissions test for seniors seeking admission to college. A random sample of 10 ACT composite scores from each school was used. The ACT composite scores follow.

Old school: / 20 / 24 / 27 / 26 / 21 / 16 / 29 / 14 / 8 / 20
New school : / 12 / 28 / 20 / 20 / 18 / 27 / 24 / 7 / 19 / 24

a.)Use a calculator to verify that while .

b.)Test the claim that there is a difference in the ACT test scores from the two schools at the5% level of significance.

4.A marketing consultant was hired to visit a random sample of five sporting goods stores across the state of California. Each store was part of a large franchise of sporting goods stores. The consultant taught the managers of each store better ways to advertise and display their goods. The net sales for one month before and one month after the consultant’s visit were recorded for each store ( in thousands of dollars) (Table 9-26).

Table 9-26Net Sales (in thousands of dollars)

Store / 1 / 2 / 3 / 4 / 5
Before visit / 57.1 / 94.6 / 49.2 / 77.4 / 43.2
After visit / 63.5 / 101.8 / 57.8 / 81.2 / 41.9

Do the data indicate that the net sales improved? (Use )

  1. Professor Hauss claims that a college algebra student can increase his or her test score if provided with sample problems in advance of the exam. To test this claim, Professor Hauss gave an exam but no advance sample problems to a random sample of 10 algebra students. The average score on this exam was 73.1 with standard deviation 6.9. She gave another random sample of 12 algebra students the same exam but also gave the students sample problems in advance. The student’s average score was 79.4 with standard deviation 8.0.

a.)Using a 1% level of significance, can we say that Professor Hauss’ claim is justified?

b.)Answer part (a) using a 5% level of significance.

6.Two competing companies make TV picture tubes. A random sample of 100 Nippon tubes showed that the average lifetime was yrs. With standard deviation 0.5 yrs. Do the data indicate that the Nippon tubes last longer? (Use a 1% level of significance.)

7.The student council is thinking about discontinuing the student poetry magazine because only 20% of the students read it. A vote was taken and it was decided to continue the magazine if more than 20% of the students are known to read it. A random sample of 256 students showed that 77 of them had read the last issue. Use a 5% level of significance to determine whether the magazine should be continued.

8.Two types of flu vaccine are being tested to determine if there is a difference in the proportion of adult patient reactions. Twelve out of a random sample of 196 adults given vaccine A had a reaction. Use a 1% level of significance to test the claim that a higher proportion of adults have a reaction to vaccine A than vaccine B.

9.The manufacturer of a sports car claims that the fuel infection system lasts 48 months before it needs to be replaced. A consumer group tests this claim by surveying a random sample of 10 owners who had the fuel injection system replace. The ages of the car at the time of replacement were (in months):

2942495853

4630514262

a.)Use your calculator to verify that the mean age of a car when the fuel injection system fails is mo. With standard deviation x = 10.85 mo.

b.)Test the claim that the fuel injection system lasts less than 48 months before needing replacement. Use a 5% level of significance.

  1. Six sets of identical twins were randomly selected from a population of identical twins. One child was taken at random from each pair to form an experimental group. These children participated in a program designed to promote creative thinking. The other child from each pair was part of the control group that did not participate in the program to promote creative thinking. At the end of the program, a creative problem-solving test was given with the results shown in Table 9-27.

Table 9-27Scores on Creative Problem-Solving Test

Twin Pair / A / B / C / D / E / F
Experimental group / 53 / 35 / 12 / 25 / 33 / 47
Control group / 39 / 21 / 5 / 18 / 21 / 42

Higher scores indicate better performance in creative problem solving. Do the data support the claim that the program of the experimental group did promote creative problem solving? (Use .)

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