Exam 3 Part 2

1.A food snack manufacturer samples 11 bags of pretzels off the assembly line and weighs their contents. If the sample mean is 13.2 oz. and the sample standard deviation is 0.60 oz., find the 95% confidence interval of the true mean. Show all work.

2. A random sample of magnesium concentrations (in parts per million, or ppm) in ground water from various locations follows. Estimate the mean concentration of magnesium in ppm with 90% confidence. Show all work. You may use your calculator to find the mean and standard deviation.

45

104

16

102

48

58

9

110

61

16

57

90

70

123

81

117

40

5

50

59

3. A survey of 800 women shoppers found that 17% of them shop on impulse. What is the 98% confidence interval for the true proportion of women shoppers who shop on impulse?

4. A manufacturer claims that its televisions have an average lifetime of at least five years (60 months) with a population standard deviation of seven months. Eighty-one televisions were selected at random, and the average lifetime was found to be 59 months. With = 0.05, is the manufacturer’s claim supported? Conduct five-step hypothesis testing.

5. Science fiction novels average 310 pages in length. The average length of 14 randomly chosen novels written by I. M. Wordy was 375 pages in length with a standard deviation of 40. At = .05, are Wordy’s novels significantly longer than the average science fiction novel?

Conduct five-step hypothesis testing.

6. Two allergists recorded the main area of allergy for new patients during a month. At , test the claim that the allergy diagnosis and the doctor that treated the patients are independent.

Allergies

Pollen

Food

Mold

Pets

Doctor 1

8

6

5

7

Doctor 2

34

6

6

24

7. From the Data Bank in Appendix D, choose two variables that you think might be related, such as exercise and weight, or IQ and educational level. Performa complete correlation and regression analysis. Use Minitab or Excel to do the calculations and the graphs, but you must still conduct the hypothesis testing.

a.

b.

c.

d.

e.

Draw a scatterplot

Compute the correlation coefficient

Use hypothesis testing to determine if r is significant.

Find the regression line if r is significant.

Summarize the results, include your personal reaction to the results.

8. Suppose a school superintendent reads an article which states that the overall mean score for the SAT is 910. He does some research and collects data on a sample of his students. He discovered that the average is 960. The superintendent calls the local newspaper to report that his students have scored much higher than the national average. Is he correct? Explain your reasoning. What else should be considered in his claim.*…*