StatTutor Lesson - Observation versus Experiment

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      Questions 1-2

      79

      Question 1.

      Which of the following is an observational study?

      		A.
      		B.
      		C.
      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.
      2

      Questions 3-6

      134

      Question 3.

      Which type of data production "imposes treatments" on subjects?

      		A.
      		B.
      		C.
      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.
      2

      Questions 7-8

      194

      Question 7.

      Did researchers assign families to live near power lines or did families self-select to live near power lines?

      		A.
      		B.
      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.
      2

      Question 9

      213

      Question 9.

      Can you conclude causation?

      		A.
      		B.
      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.
      2

      Questions 10-11

      280

      Question 10.

      Did researchers assign whether patient received Botox or salt water or did patient self-select which to receive?

      		A.
      		B.
      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 12

      298

      Question 12.

      Can you conclude causation?

      		A.
      		B.
      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.
      2

      Questions 13-14

      343

      Question 13.

      Did researchers assign subjects to drink or not drink wine, beer and/or grape juice or did subjects decide?

      		A.
      		B.
      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 15

      357

      Question 15.

      Can you conclude causation?

      		A.
      		B.
      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

      416

      Question 16.

      What does a lurking variable affect?

      		A.
      		B.
      		C.
      		D.
      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

      Questions 19-20

      543

      Question 19.

      When is a lurking variable often confounded with the explanatory variable?

      		A.
      		B.
      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