StatTutor Lesson - The Logic of Randomized Comparative Experiments

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      Questions 1-2

      106

      Question 1.

      In an experiment, how do researchers form groups that are similar before treatments are applied?

      		A.
      		B.
      		C.
      Incorrect. In theory, using a random device creates groups that are similar in all respects before treatments are applied.
      Correct. In theory, using a random device creates groups that are similar in all respects before treatments are applied.
      Incorrect. Try again.
      2

      Questions 3-6

      222

      Question 3.

      What is the purpose of a control in an experiment?

      		A.
      		B.
      		C.
      Incorrect. Without a control group, we cannot know whether the response is due to the active treatment or to chance or to something else.
      Correct. Without a control group, we cannot know whether the response is due to the active treatment or to chance or to something else.
      Incorrect. Try again.
      2

      Question 7

      304

      Question 7.

      When are results statistically significant?

      		A.
      		B.
      		C.
      Incorrect. Most people think that significant mean important. But in statistics, the term "significant" implies "too big" to be due to chance.
      Correct. Most people think that significant mean important. But in statistics, the term "significant" implies "too big" to be due to chance.
      Incorrect. Try again.
      2

      Question 8

      349

      Question 8.

      Since the difference is statistically significant, can we conclude that the vaccine prevents polio?

      		A.
      		B.
      Incorrect. Significance implies that the treatment works.
      Correct. Significance implies that the treatment works.
      Incorrect. Try again.
      2