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Chapter 8: Q 27. (page 509)

Power lines and cancer Does living near power lines cause leukemia in

children? The National Cancer Institute spent 5years and $5million gathering data on this question. The researchers compared 638children who had leukemia with 620who did not. They went into the homes and measured the magnetic fields in children’s bedrooms, in other rooms, and at the front door. They recorded facts about power lines near the family home and also near the mother’s residence when she was pregnant. Result: No association between leukemia and exposure to magnetic fields of the kind produced by power lines was found.

a. Was this an observational study or an experiment? Justify your answer.

b. Does this study prove that living near power lines doesn’t cause cancer? Explain your answer.

Short Answer

Expert verified

a. The above mentioned in an observational study.

b. No, this study doesn't prove prove that living near power lines doesn’t cause cancer.

Step by step solution

01

Given Information

Scientists compared 638children who had leukemia with 620who had not.

No association between exposure to magnetic field and leukemia was found.

02

Whether study is observational or experimental

Experimental Study is one in which certain people in group is applied treatment and other portion is not.

In observational study, without affecting people, members of sample are surveyed.

Here, afterwards, measurements are done. It's a observational study.

03

If study prove living near power lines does not cause cancer

Study should be experimental to prove cause and effect as variables are controlled that effect the result.

Hence, this study doesn't prove prove that living near power lines doesn’t cause cancer.

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Most popular questions from this chapter

t time When constructing confidence intervals for a population mean, we almost always use critical values from a t distribution rather than the standard Normal distribution.

a. When is it necessary to use a t critical value rather than a z critical value when constructing a confidence interval for a population means?

b. For a particular level of confidence, explain what happens to the t critical values as Page Number: 548 the degrees of freedom increase.

The Gallup Poll interviews 1600 people. Of these, 18% say that they jog regularly. The news report adds: “The poll had a margin of error of plus or minus three percentage points at a 95% confidence level.” You can safely conclude that

a. 95% of all Gallup Poll samples like this one give answers within ±3% of the true population value.

b. the percent of the population who jog is certain to be between 15% and 21%.

c. 95% of the population jog between 15% and 21% of the time.

d. we can be 95% confident that the sample proportion is captured by the confidence interval.

e. if Gallup took many samples, 95% of them would find that 18% of the people in the sample jog.

Losing weight Refer to Exercise 6.

a. Explain what would happen to the length of the interval if the confidence level was decreased to 90%.

b. How would a 95%confidence interval based on triple the sample size compare to the original 95%interval?

c. As Gallup indicates, the 3percentage point margin of error for this poll includes only sampling variability (what they call “sampling error”). What other potential sources of error (Gallup calls these “non sampling errors”) could affect the accuracy of the 95% confidence interval?

Good wood? A lab supply company sells pieces of Douglas fir 4 inches long and

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In preparing to construct a one-sample t interval for a population mean, suppose we are not sure if the population distribution is Normal. In which of the following circumstances would we not be safe constructing the interval based on an SRS of size14from the population?

a. A stemplot of the data is roughly bell-shaped.

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d. The sample standard deviation is large.

e. The sample standard deviation is small.
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