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A double-blind experiment was conducted to evaluate the effectiveness of the Salk polio vaccine. The purpose of keeping the diagnosing physicians unaware of the treatment status of the experimental subjects was to (a) eliminate grounds for malpractice suits. (b) ensure that subjects were randomly assigned to treatments. (c) eliminate a possible source of bias. (d) make sure nobody is harmed. (e) avoid the placebo effect.

Short Answer

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(c) eliminate a possible source of bias.

Step by step solution

01

Identifying the Purpose of a Double-Blind Experiment

A double-blind experiment is one where neither the participants nor the physicians administering the treatment know who is receiving the actual treatment or the placebo. This is done to prevent bias in the experiment results, as neither the expectations of the participants nor those of the physicians should influence the outcomes.
02

Analyzing the Given Options

Let's evaluate each given option: (a) Keeping the diagnosing physicians unaware is not meant to prevent malpractice suits. (b) Random assignment of subjects is done separately from the blindness of the experiment. (c) Unawareness of the treatment status eliminates bias that physicians might introduce. This is a key reason for conducting double-blind experiments. (d) Ensuring nobody is harmed is a general ethical concern, but not specific to being double-blind. (e) While it's related, the placebo effect pertains more to the participants being unaware, not the physicians.
03

Determining the Correct Answer

Based on the analysis, the primary reason for implementing a double-blind procedure is to eliminate a possible source of bias (as indicated in option (c)). This helps in providing objective results unaffected by any conscious or unconscious influence from either the physicians or the subjects.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Bias Reduction
In experimental research, bias can significantly impact the reliability of results. Bias refers to systematic errors that can skew data, leads to false conclusions, and ultimately invalidates the experiment's outcome. Double-blind experiments aim to reduce this by ensuring that neither the participants nor the physicians know who receives the treatment or the placebo.
When physicians are blinded, they cannot unconsciously influence the participant鈥檚 responses or the outcomes they report. Similarly, when participants do not know whether they receive the actual treatment or a placebo, their psychological expectations do not affect the results.
This process helps in achieving more accurate data, as it ensures that the observed effects are due solely to the treatment being tested rather than external factors like expectations or prejudices. By eliminating bias, researchers can confidently attribute changes in the experimental group to the treatment itself, enhancing the validity and reliability of the study.
Placebo Effect
The placebo effect is a fascinating psychological phenomenon where patients experience real changes in their symptoms simply because they believe they are receiving treatment. In medical studies, this means that improvements can occur not necessarily because a treatment is effective, but because the person believes it is.
Double-blind experiments help control for the placebo effect by ensuring participants do not know if they're receiving the treatment or a placebo. The expectation of treatment can sometimes lead to observable changes, even in the absence of an active medical intervention. By blinding participants, researchers can more accurately assess the true efficacy of the treatment being studied.
  • This control helps to differentiate between actual therapeutic effects and psychological ones.
  • Understanding and accounting for placebo effects is crucial in evaluating new treatments, ensuring that positive results are due to the treatment itself.
Experimental Design
Experimental design is a crucial element in conducting scientific research. It refers to the structured and systematic approach scientists use to test hypotheses and gather data. A well-designed experiment effectively reduces errors and biases, leading to more accurate and reliable results.
In designing an experiment, researchers often utilize methods like randomization, control groups, and blinding to enhance the integrity of their studies. Randomization involves randomly assigning subjects to different treatment groups to ensure each group is comparable, minimizing selection bias.
Double-blind experiments are a sophisticated part of experimental design, combining two levels of blinding to minimize bias from both participants and researchers. Control groups, often given a placebo, act as a standard to compare the effects of the active treatment.
Careful experimental design is vital for producing conclusive data. It allows researchers to isolate variables and determine causality, ensuring that findings are both valid and reproducible across different contexts.

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Most popular questions from this chapter

Dr. Linda Stern and her colleagues recruited 132 obese adults at the Philadelphia Veterans Affairs Medical Center in Pennsylvania. Half of the participants were randomly assigned to a low-carbohydrate diet and the other half were assigned to a low-fat diet. Researchers measured each participant鈥檚 change in weight and cholesterol level after six months and again after one year. Subjects in the low-carb diet group lost significantly more weight than subjects in the low-fat diet group during the first six months of the study. At the end of a year, however, the average weight loss for subjects in the two groups was not significantly different.\(^{42}\) (a) Why did researchers randomly assign the subjects to the diet treatments? (b) Explain to someone who knows little statistics what 鈥渓ost significantly more weight鈥 means. (c) The subjects in the low-carb diet group lost an average of 5.1 kg in a year. The subjects in the low-fat diet group lost an average of 3.1 kg. Explain how this information could be consistent with the fact that weight loss in the two groups was not significantly different.

Random sampling versus random assignment Explain the difference between the types of inference that can be made as a result of random sampling and random assignment.

What kind of error? Which of the following are sources of sampling error and which are sources of nonsampling error? Explain your answers. (a) The subject lies about past drug use. (b) A typing error is made in recording the data. (c) Data are gathered by asking people to mail in a coupon printed in a newspaper.

Comment on each of the following as a potential sample survey question. Is the question clear? Is it slanted toward a desired response? (a) Which of the following best represents your opinion on gun control? 1\. The government should confiscate our guns. 2\. We have the right to keep and bear arms. (b) A freeze in nuclear weapons should be favored because it would begin a much-needed process to stop everyone in the world from building nuclear weapons now and reduce the possibility of nuclear war in the future. Do you agree or disagree?

Suppose 1000 iPhones are produced at a factory today. Management would like to ensure that the phones鈥 display screens meet their quality standards before shipping them to retail stores. Since it takes about 10 minutes to inspect an individual phone鈥檚 display screen, managers decide to inspect a sample of 20 phones from the day鈥檚 production. (a) Explain why it would be difficult for managers to inspect an SRS of 20 iPhones that are produced today. (b) An eager employee suggests that it would be easy to inspect the last 20 iPhones that were produced today. Why isn鈥檛 this a good idea? (c) Another employee recommends inspecting every fiftieth iPhone that is produced. Explain carefully why this sampling method is not an SRS.

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