Chapter 1. 1·11–1·14 Well-designed experiments are essential to testing hypotheses.

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You must read each slide, and complete any questions on the slide, in sequence.

Instructions

Check your understanding of concepts from 1·11–1·14 Well-designed experiments are essential to testing hypotheses by answering the following questions.

1.

1. In blind experimental design:

the experimenter does not know which (if any) treatment the subjects are receiving.

the experimenter does not influence the experiment's outcome.

the experimental subjects do not know which (if any) treatment they are receiving.

a placebo is used.

the subjects are randomly assigned into experimental and control groups.

Correct! (See section 1·11 Controlling variables makes experiments more powerful.)

Incorrect. (See section 1·11 Controlling variables makes experiments more powerful.)

2.

2. In 2001, the journal Behavioral Ecology changed its policy for reviewing manuscripts submitted for publication. Its new policy instituted a double-blind process, whereby neither the reviewers' nor the authors' identities were revealed. Previously, the policy had been a single-blind process in which reviewers' identities were kept secret, but the authors' identities were known to the reviewers. In an analysis of papers published between 1997 and 2005, it turned out that after 2001, when the double-blind policy took effect, there was a significant increase in the number of published papers in which the first author was female. Analysis of papers in a similar journal that maintain the single-blind process over that period revealed no such increase. This study reveals that:

scientists may have biases—sometimes subconscious—that influence their behavior.

males should not be reviewers for papers submitted to scientific journals.

that better papers whose first authors were female were submitted to Behavioral Ecology than to the other journal.

female scientists began doing better work beginning in 2001.

scientists should not be reviewers for papers submitted to scientific journals.

Correct! (See section 1·14 We’ve got to watch out for our biases.)

Incorrect. (See section 1·14 We’ve got to watch out for our biases

3.

3. Before experimental drugs can be brought to market, they must undergo many rigorous trials to ensure they deliver their medical benefits effectively and safely. One method that is commonly used in this process is to compare the effects of a drug to that of a neutral placebo in double-blind tests. Which of the following choices correctly describes a double-blind test?

The researchers apply two layers of blindfolds to the study's participants so they can not know if they are receiving the drug or a placebo.

The researchers do not know who receives the drug or the placebo but the participants know and tell them later.

The researchers know who is receiving the drug and who is receiving the placebo but do not know what the supposed effects of the drug should be.

Neither the researchers nor the study's participants know who is receiving the drug and who is receiving the placebo.

None of the above descriptions is correct.

Correct! (See section 1·11 Controlling variables makes experiments more powerful.)

Incorrect. (See section 1·11 Controlling variables makes experiments more powerful.)

4.

4. In the late 1950s, a doctor reported in the Journal of the American Medical Association that stomach ulcers could be effectively treated by having a patient swallow a balloon connected to some tubes that circulated a refrigerated fluid. He argued that, by super-cooling the stomach, acid production was reduced and the ulcer relieved. All 24 of his patients who received the treatment were healed. Why does this fall short of qualifying as an example of the scientific method?

There was no control group with which to compare his patients who received the treatment.

There were not enough experimental subjects to draw a definitive conclusion.

All of the patients were aware of the treatment they received.

Although there was a control group, it was not randomly selected.

All of the above are correct.

Correct! (See section 1·11 Controlling variables makes experiments more powerful.)

Incorrect. (See section 1·11 Controlling variables makes experiments more powerful.)

5.

5. A biologist was concerned about the environmental effects of an insecticide being used in his area to kill mosquitos that carried equine encephalitis. He decided to study the environmental impact of this herbicide on blue jay reproduction. He selected two small habitats with similar vegetation and similar-sized blue jay populations (about 120 birds) with equal reproductive rates. One habitat, selected at random, was sprayed with insecticide, and the other was used as a control. Blue jay reproduction rates were measured in both habitats before and after the treatment. What is the MOST IMPORTANT flaw in this investigation?

lack of randomization

poor outcome measure

There are no important flaws in this investigation.

lack of controls

lack of replication

Correct! (See section 1·13 Repeatable experiments increase our confidence.)

Incorrect. (See section 1·13 Repeatable experiments increase our confidence.)

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