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Chapter 2: Problem 59

The article "A Debate in the Dentist's Chair" (San Luis Obispo Tribune, January 28,2000 ) described an ongoing debate over whether newer resin fillings are a better alternative to the more traditional silver amalgam fillings. Because amalgam fillings contain mercury, there is concern that they could be mildly toxic and prove to be a health risk to those with some types of immune and kidney disorders. One experiment described in the article used sheep as subjects and reported that sheep treated with amalgam fillings had impaired kidney function. a. In the experiment, a control group of sheep that received no fillings was used but there was no placebo group. Explain why it is not necessary to have a placebo group in this experiment. b. The experiment compared only an amalgam filling treatment group to a control group. What would be the benefit of also including a resin filling treatment group in the experiment? c. Why do you think the experimenters used sheep rather than human subjects?

Short Answer

Expert verified
a. A placebo group is not necessary in this experiment because the sheep would not have any psychological expectations about the fillings possibly affecting their kidney function. b. Including a resin filling treatment group would allow comparison between the two types of fillings and help determine if resin fillings also cause impaired kidney function. c. The experimenters likely used sheep instead of humans for ethical reasons, to avoid potential health risks, and for practical reasons such as easier control over diet and environment.

Step by step solution

01

Understanding Control and Placebo Groups

A control group is the group in an experiment or study that does not receive treatment by the researchers and is used as a benchmark to measure the effects of that treatment. On the other hand, a placebo group is similar to the control group, but the subjects are given an 'ineffective' or 'fake' treatment. This is often done to eliminate the placebo effect, where just thinking that treatment has been received can actually improve a condition.
02

Answering Part (a)

In this particular experiment involving sheep, a placebo group isn't necessary because the sheep wouldn't have any psychological expectations about the fillings possibly affecting their kidney function. This means there's no placebo effect to control for in this experiment.
03

Answering Part (b)

Including a resin filling treatment group in addition to the amalgam filling treatment group can allow comparison between the two types of fillings. This way, one can see if resin fillings, like amalgam fillings, also cause impaired kidney function or if they are safer.
04

Answering Part (c)

The experimenters likely used sheep instead of human subjects for ethical and practical reasons. Because the study involves potentially harmful substances (i.e., mercury in amalgam fillings), it wouldn't be ethically permissible to use human subjects, especially given the health risks. Additionally, practical reasons may include availability and cost, as well as easier control over the diet and environment of the sheep, which could affect the outcomes.

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