AP Statistics : How to establish blind experiments

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #1 : How To Establish Blind Experiments

A study is attempting to test various brands of cola against each other. Which of these would not be a measure that could be used to help create a double blind test?

Possible Answers:

Removing or covering up the labels on the cans or bottles.

Randomizing the placement of the cola samples.

Serving the samples to the taster in their usual containers.

Filling the sample cups the same way.

Making sure the test administrator also does not know the brand of each sample until after the test.

Correct answer:

Serving the samples to the taster in their usual containers.

Explanation:

Remember that a double blind experiment means that neither the subject nor the person conducting the experiment knows the identity of the various treatments until the test is over, so as to minimize bias.

Therefore of the options,

serving the samples to the taster in their usual containers, is the one which would not help create a double blind test.

Example Question #2 : How To Establish Blind Experiments

Which of the following is an example of a double blind experiment? 

Possible Answers:

An experiment in which test subjects know which therapy they are receiving, but researchers are unaware

None of these are an example of a double blind experiment

An experiment in which both test subjects and researchers are aware of who is receiving the treatment and who is receiving the placebo

An experiment in which neither the test subjects nor the researchers know who is receiving the treatment and who is receiving the placebo

An experiment in which researchers know which therapy test subjects are receiving, but test subjects are unaware 

Correct answer:

An experiment in which neither the test subjects nor the researchers know who is receiving the treatment and who is receiving the placebo

Explanation:

A double blind experiment requires that both researchers and test subjects are unaware of who is receiving the treatment and who is receiving the placebo. If only one group is unaware, it is a single blind experiment. If both groups are aware, the experiment is not blinded.

Example Question #21 : How To Conduct An Experiment

Which of the following is an example of a single-blind experiment? 

Possible Answers:

An experiment in which the researchers are aware of who is receiving a placebo and who is receiving a therapy, but the test subjects are unaware.

An experiment in which the test subjects are aware of who is receiving a placebo and who is receiving a therapy, but the researchers are unaware. 

An experiment in which the researchers and test subjects are aware of who is receiving a placebo and who is receiving a therapy.

An experiment in which the researchers and test subjects are unaware of who is receiving a placebo and who is receiving a therapy. 

Two of the answers are correct

Correct answer:

Two of the answers are correct

Explanation:

In a single-blind experiment, one group (either the researchers or the test subjects) must be blinded while the other group is aware of who is receiving a placebo and who is receiving a therapy.

The following two examples are correct:

-An experiment in which the test subjects are aware of who is receiving a placebo and who is receiving a therapy, but the researchers are unaware. 

-An experiment in which the researchers are aware of who is receiving a placebo and who is receiving a therapy, but the test subjects are unaware.

Example Question #22 : How To Conduct An Experiment

Alpha Corporation developed a new pill to treat elevated glucose levels. They want to test the efficiency of the pill to lower glucose levels by gathering a sample of people with high glucose and giving them either:

1) A daily dose of their new pill ("Experimental Group")

2) A daily placebo pill that looks the same but does not do anything ("Placebo Group")

 

How can they make this a "Blind Study"?

Possible Answers:

Give all participants both pills.

Give the pill to people with high blood glucose and low blood glucose.

Blindfold the participants while they take the pills.

Keep the participant identities hidden from the experimenters permanently.

Randomly sort people into the Experimental or Placebo groups, without letting them know which pill they received.

Correct answer:

Randomly sort people into the Experimental or Placebo groups, without letting them know which pill they received.

Explanation:

A blind experiment is one in which the participant does not know which experimental group they are in-- which is accomplished by not letting them know if they are in the Experimental or Placebo group.

 

Example Question #23 : How To Conduct An Experiment

A drug company wants to test a new pill that should make people's nails grow twice as quickly as normal. How can they make the study a blind study?

Possible Answers:

Give all participants the placebo pill and measure nail growth.

This test cannot be done as a blind study.

Give one group of people the actual pill and one group a placebo, but don't tell the participants which pill they are receiving.

Give all participants the actual pill and measure nail growth.

Give half participants the placebo pill and tell them they had the actual pill, and give the rest the actual pill but tell them they have the placebo pill.

Correct answer:

Give one group of people the actual pill and one group a placebo, but don't tell the participants which pill they are receiving.

Explanation:

In order for a study to be "blind," the participants can't know which group they are sorted into. For a study to be double-blind, which is even better, the researchers should also be blind to which group participants are in until the study is completed.

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