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Chapter 4: Q 63. (page 255)

Treating prostate disease A large study used records from Canada鈥檚 national health care system to compare the effectiveness of two ways to treat prostate

disease. The two treatments are traditional surgery and a new method that does not require surgery. The records described many patients whose doctors had

chosen each method. The study found that patients treated by the new method were significantly more likely to die within eight years.

(a) Further study of the data showed that this conclusion was wrong. The extra deaths among patients who got the new method could be explained by lurking variables. What lurking variables might be confounded with a doctor鈥檚 choice of surgical or nonsurgical treatment?

(b) You have 300prostate patients who are willing to serve as subjects in an experiment to compare the two methods. Write a few sentences describing how you would design this experiment.

Short Answer

Expert verified

(a) The lurking variables here are cost, patient's health, no possibility of survival.

(b) Divide patients into two groups and allow traditional procedure to one patient and modern method to other. Conclude the result.

Step by step solution

01

Given Information

Two treatments were given to the patients, one traditional method and one modern without surgery. The study found that patients treated by the new method were significantly more likely to die within eight years.

02

To determine lurking variables may be misunderstood for surgical and treatment without surgery.

The lurking variable has major effect, but it is not an indicator. It may be omitted if its presence is unclear. Because of it, patient may be bad state and less chances of survival. As a result may not suggest surgery and prefer non operative means.

Cost, health are other lurking variables.

03

To elaborate how to plan experiment

  • Assign two groups of 150each to the patients randomly.
  • Give one group traditional treatment and other modern treatment.
  • Measure the number of patients survived without surgery in two groups.

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Most popular questions from this chapter

Headache relief Doctors identify 鈥渃hronic tension- type headaches鈥� as headaches that occur almost daily for at least six months. Can antidepressant medications or stress management training reduce the number and severity of these headaches? Are both together more effective than either alone? Investigators compared four treatments: antidepressant alone, placebo alone, antidepressant plus stress management, and placebo plus stress management. The headache sufferers named in the following table have agreed to participate in the study.

(a) Outline the design of the experiment. What is this type of design called?

(b) Explain how you would randomly assign the subjects to the four treatment groups. Then carry out your random assignment.

The manager of a sports arena wants to learn more about the financial status of the people who are attending an NBA basketball game. He would like to give a survey to a representative sample of the more than 20,000 fans in attendance. Ticket prices for the game vary a great deal: seats near the court cost over \(100 each, while seats in the top rows of the arena cost \)25 each. The arena is divided into 30 numbered sections, from 101 to 130 Each section has rows of seats labeled with letters from A (nearest the court) to ZZ (top row

of the arena).

In an interesting experiment, researchers examined the effect of ultrasound on birth weight. Pregnant women participating in the study were randomly assigned to one of two groups. The first group of women received an ultrasound; the second group did not. When the subjects鈥� babies were born, their birth weights were recorded. The women who received the ultrasounds had heavier babies.

Was the experiment double-blind? Why is this important?

An example of a non-sampling error that can reduce the accuracy of a sample survey is

(a) using voluntary response to choose the sample.

(b) using the telephone directory as the sampling frame.

(c) interviewing people at shopping malls to obtain a sample.

(d) variation due to chance in choosing a sample at random.

(e) inability to contact many members of the sample.

In the cornfield An agriculture researcher wants to compare the yield of five corn varieties: A, B, C, D, and E. The field in which the experiment will be carried out increases in fertility from north to south. The researcher therefore divides the field into twenty five plots of equal size, arranged in five east鈥搘est rows of five plots each, as shown in the diagram.

(a) Explain why a randomized block design would be better than a completely randomized design in this setting.

(b) Should the researcher use the rows or the columns of the field as blocks? Justify your answer.

(c) Use technology or Table D to carry out the random assignment required by your design. Explain your method clearly.
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