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Chapter 4: Q. R4.5 (page 288)

The National Halothane Study was a major investigation of the safety of anesthetics used in surgery. Records of over 850,000operations performed in 34major hospitals showed the following death rates for four common anesthetics:

There seems to be a clear association between the anesthetic used and the death rate of patients. Anesthetic C appears to be more dangerous.

a. Explain why we call the National Halothane Study an observational study rather than an experiment, even though it compared the results of using different anesthetics in actual surgery.

b. Identify the explanatory and response variables in this study.

c. When the study looked at other variables that are related to a doctor鈥檚 choice of anesthetic, it found that Anesthetic C was not causing extra deaths. Explain the concept of confounding in this context and identify a variable that might be confounded with the doctor鈥檚 choice of anesthetic.

Short Answer

Expert verified

a. Since records are used, no treatment was deliberately imposed on individuals and thus the study is an observational study.

b. The experimental variable is the anaesthetics and the response variable is the effect of the anaesthetic that is the death rate.

c. The type of the surgery is the variable.

Step by step solution

01

Part (a) Step 1. Explanation

The National Halothane study an observational study rather than an experiment even though it compared the results of using different anaesthetics in actual surgery because An experiment deliberately imposes some treatment on individuals in order to observe their responses. An observational study tries to gather information without disturbing the scene they are observing.

Since records are used, no treatment was deliberately imposed on individuals and thus the study is an observational study.

02

Part (b) Step 1. Explanation

The explanatory variable is the one that is changed in order to see the effect on the response variable.

The experimental variable is the anaesthetics used in the surgery because it is used in the experiment and its result is the response variable is the effect of the anaesthetic that is the death rate controlled by the anaesthetics.

03

Part (c) Step 1. Explanation

Variables are confounded when their effects on a response variable cannot be distinguished. One possible confounding variable is type of surgery. If one anaesthesia is used more often with a type of surgery that has a higher death rate anyway, we wouldn鈥檛 know if the death rate was higher because of the anaesthesia type or the surgery type.

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Most popular questions from this chapter

You wonder if TV ads are more effective when they are longer or repeated more often

or both. So you design an experiment. You prepare 30-second and 60-second ads for a

camera. Your subjects all watch the same TV program, but you assign them at random

to four groups. One group sees the 30-second ad once during the program; another sees

it three times; the third group sees the 60-second ad once; and the last group sees the

60-second ad three times. You ask all subjects how likely they are to buy the camera.

Which of the following best describes the design of this experiment?

a. This is a randomized block design, but not a matched pairs design.

b. This is a matched pairs design.

c. This is a completely randomized design with one explanatory variable (factor).

d. This is a completely randomized design with two explanatory variables (factors).

e. This is a completely randomized design with four explanatory variables (factors).

Side effects Even if an experiment is double-blind, the blinding might be compromised if side effects of the treatments differ. For example, suppose researchers at a skin-care company are comparing their new acne treatment against that of the leading competitor. Fifty subjects are assigned at random to each treatment, and the company鈥檚 researchers will rate the improvement for each of the 100subjects. The researchers aren鈥檛 told which subjects received which treatments, but they know that their new acne treatment causes a slight reddening of the skin. How might this knowledge compromise the blinding? Explain why this is an important consideration in the experiment.

Wording bias Comment on each of the following as a potential sample survey question.

Is the question clear? Is it slanted toward a desired response?

a. 鈥淪ome cell phone users have developed brain cancer. Should all cell phones come with

a warning label explaining the danger of using cell phones?鈥�

b. 鈥淒o you agree that a national system of health insurance should be favored because it

would provide health insurance for everyone and would reduce administrative costs?鈥�

c. 鈥淚n view of escalating environmental degradation and incipient resource depletion,

would you favor economic incentives for recycling of resource鈥搃ntensive consumer

驳辞辞诲蝉?鈥�

A local news agency conducted a survey about unemployment by randomly dialing phone

numbers during the work day until it gathered responses from 1000 adults in its state. In

the survey, 19% of those who responded said they were not currently employed. In reality,

only 6% of the adults in the state were not currently employed at the time of the survey.

Which of the following best explains the difference in the two percentages?

a. The difference is due to sampling variability. We shouldn鈥檛 expect the results of a

random sample to match the truth about the population every time.

b. The difference is due to response bias. Adults who are employed are likely to lie and

say that they are unemployed.

c. The difference is due to undercoverage bias. The survey included only adults and did

not include teenagers who are eligible to work.

d. The difference is due to nonresponse bias. Adults who are employed are less likely to

be available for the sample than adults who are unemployed.

e. The difference is due to voluntary response. Adults are able to volunteer as a member

of the sample.

More oil and inflammation Refer to Exercise 55. Could blinding be used in this experiment? Explain your reasoning. Why is blinding an important consideration in this context?

See all solutions

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