Chapter 1. Randomized Comparative Experiments

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Questions 1-2

0:47

Question 1.1

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Incorrect. Confounding is usually not a desired principle of a good experiment.
Correct. Confounding is usually not a desired principle of a good experiment.
Incorrect. Try again.
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Question 1.2

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Incorrect. In an experiment, randomization has to do with randomly assigning subjects to treatments. Randomization in a survey has to do with randomly selecting the individuals to be in the survey.
Correct. In an experiment, randomization has to do with randomly assigning subjects to treatments. Randomization in a survey has to do with randomly selecting the individuals to be in the survey.
Incorrect. Try again.
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Questions 3-4

1:52

Question 1.3

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Incorrect. Without a control and randomization, a researcher will not know if the treatment worked or if a lurking variable affected the response variable.
Correct. Without a control and randomization, a researcher will not know if the treatment worked or if a lurking variable affected the response variable.
Incorrect. Try again.
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Question 1.4

LfoUhnttGj0M2vH/ofEPzw8GyahVBOG+EVRFc6dt/tp7JyMD2BOlu+6mLT6cZXYI1zVb7giU1eHUTjJ2e+fedqZit/PLrlTouz68ksqr5aQ1z9qSjTQeO8C5om1QErRog9Rlioap/E5IPPtiVO1oxbz75+/MeCnTQFtwyF46Ya7hjEwa3AHQP5f9FqtqT5oWtsl8HqMHAhDLARyBc/+reUHxNiVDnCP8RaKUxZclvasa68/u1DAZ5/g1HbRv7BojMX8wfcTL67+g3JYAAt2K5K8XvGl4hlBW
Incorrect. Comparing two active treatments only tells us which treatment works best. It doesn't tell us if the treatments work.
Correct. Comparing two active treatments only tells us which treatment works best. It doesn't tell us if the treatments work.
Incorrect. Try again.
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Question 5

2:24

Question 1.5

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Incorrect. Randomization in an experiment is using chance to assign subjects to treatments
Correct. Randomization in an experiment is using chance to assign subjects to treatments
Incorrect. Try again.
2

Question 6

2:42

Question 1.6

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Incorrect. In order to measure variation, we must have at least two individuals receive each treatment. Repeating the entire experiment is NOT what is meant by replication in an experiment.
Correct. In order to measure variation, we must have at least two individuals receive each treatment. Repeating the entire experiment is NOT what is meant by replication in an experiment.
Incorrect. Try again.
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Questions 7-8

3:50

Question 1.7

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Incorrect. A well-designed survey does not provide evidence of cause and effect due to potential lurking variables.
Correct. A well-designed survey does not provide evidence of cause and effect due to potential lurking variables.
Incorrect. Try again.
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Question 1.8

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Incorrect. Without randomization, there could be bias and/or confounding. In addition, laws of probability cannot be applied.
Correct. Without randomization, there could be bias and/or confounding. In addition, laws of probability cannot be applied.
Incorrect. Try again.
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Questions 9-10

4:54

Question 1.9

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Incorrect. All of the above are problems that could result from not having randomization in a study.
Correct. All of the above are problems that could result from not having randomization in a study.
Incorrect. Try again.
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Question 1.10

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Incorrect. Without randomization, cause and effect should not be concluded.
Correct. Without randomization, cause and effect should not be concluded.
Incorrect. Try again.
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Questions 11-12

5:45

Question 1.11

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Incorrect. Observational studies usually have control/comparison and replication; they lack random assignment of subjects to treatments.
Correct. Observational studies usually have control/comparison and replication; they lack random assignment of subjects to treatments.
Incorrect. Try again.
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Question 1.12

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Incorrect. The media often reports a cause and effect relationship even though randomization is missing.
Correct. The media often reports a cause and effect relationship even though randomization is missing.
Incorrect. Try again.
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Questions 13-15

7:22

Question 1.13

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Incorrect. Because a new diet is compared with a standard diet, there is control/comparison.
Correct. Because a new diet is compared with a standard diet, there is control/comparison.
Incorrect. Try again.
2

Question 1.14

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Incorrect. The rats are assigned at random to the two groups.
Correct. The rats are assigned at random to the two groups.
Incorrect. Try again.
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Question 1.15

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Incorrect. There are two or more rats in each group - in fact, there are 15 rats in each group.
Correct. There are two or more rats in each group - in fact, there are 15 rats in each group.
Incorrect. Try again.
2

Question 16

8:04

Question 1.16

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Incorrect. Valid randomization requires that a random device be used to assign rats to treatments. In this case, a random digit table was used to select 15 rats.
Correct. Valid randomization requires that a random device be used to assign rats to treatments. In this case, a random digit table was used to select 15 rats.
Incorrect. Try again.
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Questions 17-18

8:43

Question 1.17

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Incorrect. Weight gain was measured on each rat, so that is the response variable. "Mean weight gain" is an aggregate measure on 15 rats, not on each rat, so it is not the response variable.
Correct. Weight gain was measured on each rat, so that is the response variable. "Mean weight gain" is an aggregate measure on 15 rats, not on each rat, so it is not the response variable.
Incorrect. Try again.
2

Question 1.18

lJ3Maid+hN+qR/tXjG31+NvAg0IaYjxFMHxnUpipJiBfYCplvPQ+h+A02SswrTNF1+ikNgothlMr8FY1j0jSA7kPHaqJ4WtMvHdSL7tw0bUT56uS0vPNO9uDJlGbh3NUXouOYZq20f7/aDHc+gv/AWGKSaK5rXUF8+PD3ActNm+1Za42ZNJDDfFXuFl7Y8d8hYtIscY2A0uSnvc+cjI59IRrM6A1sCb3z1f5onpLq8uV2fStOnXGneoQas48uQbOf6bEPIrUkLbWCT/ba8MltAtlNyE=
Incorrect. Whenever the response variable is quantitative, means are compared. Whenever the response variable is categorical, percentages are compared.
Correct. Whenever the response variable is quantitative, means are compared. Whenever the response variable is categorical, percentages are compared.
Incorrect. Try again.
2

Question 19

8:50

Question 1.19

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Incorrect. Most importantly, this study incorporates random assignment of rats to type of diet.
Correct. Most importantly, this study incorporates random assignment of rats to type of diet.
Incorrect. Try again.
2

Question 20

9:26

Question 1.20

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Incorrect. This is a correct statement.
Correct. This is a correct statement.
Incorrect. Try again.
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