Chapter 1. Observation versus Experiment

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Questions 1-2

1:19

Question 1.1

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Incorrect. Since individuals in a simple random sample are merely asked questions and not given treatments, a simple random sample is an observational study.
Correct. Since individuals in a simple random sample are merely asked questions and not given treatments, a simple random sample is an observational study.
Incorrect. Try again.
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Question 1.2

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Incorrect. Individuals in a survey are not assigned to a treatment and can self-select their treatments.
Correct. Individuals in a survey are not assigned to a treatment and can self-select their treatments.
Incorrect. Try again.
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Questions 3-6

2:14

Question 1.3

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Incorrect. In a valid experiment, subjects are randomly assigned to a treatment and then receive that treatment.
Correct. In a valid experiment, subjects are randomly assigned to a treatment and then receive that treatment.
Incorrect. Try again.
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Question 1.4

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Incorrect. Appropriate data collection always requires randomization.
Correct. Appropriate data collection always requires randomization.
Incorrect. Try again.
2

Question 1.5

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Incorrect. In surveys, individuals are randomly selected.
Correct. In surveys, individuals are randomly selected.
Incorrect. Try again.
2

Question 1.6

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Incorrect. In a valid experiment, subjects are randomly assigned to treatment groups.
Correct. In a valid experiment, subjects are randomly assigned to treatment groups.
Incorrect. Try again.
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Questions 7-8

3:14

Question 1.7

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Incorrect. The families decided where they wanted to live. Ethically, no one can tell a person where they have to live.
Correct. The families decided where they wanted to live. Ethically, no one can tell a person where they have to live.
Incorrect. Try again.
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Question 1.8

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Incorrect. Because families self-selected where they lived, this is an observational study.
Correct. Because families self-selected where they lived, this is an observational study.
Incorrect. Try again.
2

Question 9

3:33

Question 1.9

B/5sEsJ+VlhvFpjCPsjmJOoClJMOnlFR1IacKWf3uqZpgORCi23FZ4ISLu8=
Incorrect. Because this is an observational study, not an experiment, causation cannot be concluded.
Correct. Because this is an observational study, not an experiment, causation cannot be concluded.
Incorrect. Try again.
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Questions 10-11

4:40

Question 1.10

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Incorrect. The article says, "Researchers gave 322 patients underarm injections of either Botox or salt water." From this, we conclude that the researchers decided which type of injection a patient received.
Correct. The article says, "Researchers gave 322 patients underarm injections of either Botox or salt water." From this, we conclude that the researchers decided which type of injection a patient received.
Incorrect. Try again.
2

Question 1.11

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Incorrect. Since the researcher decided which type of injection a patient received, this is an experiment.
Correct. Since the researcher decided which type of injection a patient received, this is an experiment.
Incorrect. Try again.
2

Question 12

4:58

Question 1.12

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Incorrect. Since this study is an experiment, you can conclude causation.
Correct. Since this study is an experiment, you can conclude causation.
Incorrect. Try again.
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Questions 13-14

5:43

Question 1.13

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Incorrect. Since subjects were asked about their drinking habits, we can assume they were not assigned to treatments.
Correct. Since subjects were asked about their drinking habits, we can assume they were not assigned to treatments.
Incorrect. Try again.
2

Question 1.14

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Incorrect. Since subjects decided what they drank, this is an observational study.
Correct. Since subjects decided what they drank, this is an observational study.
Incorrect. Try again.
2

Question 15

5:57

Question 1.15

B/5sEsJ+VlhvFpjCPsjmJOoClJMOnlFR1IacKWf3uqZpgORCi23FZ4ISLu8=
Incorrect. Since this study is an observational study, causation cannot be concluded.
Correct. Since this study is an observational study, causation cannot be concluded.
Incorrect. Try again.
2

Questions 16-18

6:56

Question 1.16

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Incorrect. A lurking variable affects the relationship between the response variable and the explanatory variable.
Correct. A lurking variable affects the relationship between the response variable and the explanatory variable.
Incorrect. Try again.
2

Question 1.17

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Incorrect. When the effects of two variables on the response variable cannot be separated, we say that the two variables are "confounded'"
Correct. When the effects of two variables on the response variable cannot be separated, we say that the two variables are "confounded."
Incorrect. Try again.
2

Question 1.18

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Incorrect. Since confounding happens when the effects of two variables "on the response variable" cannot be separated, the response variable cannot be one of the two variables.
Correct. Since confounding happens when the effects of two variables "on the response variable" cannot be separated, the response variable cannot be one of the two variables.
Incorrect. Try again.
2

Questions 19-20

9:03

Question 1.19

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Incorrect. Because subjects in an observational study self-select their treatment, often a lurking variable becomes confounded with the explanatory variable as part of this selection.
Correct. Because subjects in an observational study self-select their treatment, often a lurking variable becomes confounded with the explanatory variable as part of this selection.
Incorrect. Try again.
2

Question 1.20

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Incorrect. When individuals in one category of one variable are all in one category of another variable, the effects of the two variables cannot be "separated."
Correct. When individuals in one category of one variable are all in one category of another variable, the effects of the two variables cannot be "separated."
Incorrect. Try again.
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