Experimental Design

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Study Notes and Guide for the AP Statistics Exam Theme 2

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Experimental Design

  1. 1. Study Session Experimental Design
  2. 2. Experimental Design <ul><li>1. Which of the following is true regarding the difference between an observational study and and an experiment? </li></ul><ul><li>a) An experiment must have a control group whereas the observational study does not. </li></ul><ul><li>b) An observational study is used for human subjects whereas an experiment is used for non-human subjects. </li></ul><ul><li>c) In an experiment, the investigator randomly places subjects into treatment and control groups whereas in an observational study, the subjects are placed into groups based on a characteristic. </li></ul><ul><li>d) The observational study can produce causal results whereas an experiment can only identify an association. </li></ul><ul><li>e) None of these is true. </li></ul>
  3. 3. Experimental Design <ul><li>Which of the following is true regarding the difference between an observational study and and an experiment? </li></ul><ul><li>c) In an experiment, the investigator randomly places subjects into treatment and control groups whereas in an observational study, the subjects are placed into groups based on a characteristic. </li></ul>
  4. 4. Experimental Design <ul><li>What are the three principles of experimental design? </li></ul>
  5. 5. Experimental Design <ul><li>What are the three principles of experimental design? </li></ul><ul><li>Randomization </li></ul><ul><li>Control </li></ul><ul><li>Replication </li></ul>
  6. 6. Experimental Design <ul><ul><li>3. In an experiment, if two variable are confounded, which of the following statements is true? </li></ul></ul><ul><ul><li>a) One of the variables must be a lurking variable. </li></ul></ul><ul><ul><li>b) There is a clear indication that a placebo effect is present in the experiment. </li></ul></ul><ul><ul><li>c) The investigator cannot separate the effect of the variables on a response variable. </li></ul></ul><ul><ul><li>d) None of these is true. </li></ul></ul>
  7. 7. Experimental Design <ul><ul><li>In an experiment, if two variable are confounded, which of the following statements is true? </li></ul></ul><ul><ul><li>c) The investigator cannot separate the effect of the variables on a response variable. </li></ul></ul>
  8. 8. Experimental Design <ul><li>Which one of the following statements about experiments is true? </li></ul><ul><li>a) All experiments must have a control group. </li></ul><ul><li>b) Blocking is employed to reduce variation. </li></ul><ul><li>c) Random assignment is only critical for treatment groups, as opposed to control groups. </li></ul><ul><li>d) Matching can be used in any experiment to eliminate lurking variables. </li></ul><ul><li>e) None of these is true. </li></ul>
  9. 9. Experimental Design <ul><li>Which one of the following statements about experiments is true? </li></ul><ul><li>b) Blocking is employed to reduce variation. </li></ul>
  10. 10. Experimental Design <ul><li>A randomized block design is similar to which </li></ul><ul><li>of the following sampling designs? </li></ul><ul><li>a) simple random sample </li></ul><ul><li>b) multi-stage cluster sample </li></ul><ul><li>c) stratified sample </li></ul><ul><li>d) convenience sample </li></ul><ul><li>e) systematic sample </li></ul><ul><li>  </li></ul>
  11. 11. Experimental Design <ul><li>A randomized block design is similar to which </li></ul><ul><li>of the following sampling designs? </li></ul><ul><li>c) stratified sample </li></ul><ul><li>  </li></ul>
  12. 12. Experimental Design <ul><li>Blocking is utilized to help </li></ul><ul><li>a) organize the treatment and control groups </li></ul><ul><li>b) counteract the placebo effect. </li></ul><ul><li>c) produce groups that are as similar as possible. </li></ul><ul><li>d) avoid the need for randomization. </li></ul><ul><li>e) replicate the experiment within each block </li></ul>
  13. 13. Experimental Design <ul><li>Blocking is utilized to help </li></ul><ul><li>c) produce groups that are as similar as possible. </li></ul>
  14. 14. Experimental Design <ul><li>A randomized block design is NOT </li></ul><ul><li>a) similar to a stratified random sample for surveys </li></ul><ul><li>b) a strategy to control for an influence that would </li></ul><ul><li>affect the outcome of the experiment., </li></ul><ul><li>c) a strategy that depends on randomization. </li></ul><ul><li>d) only used for gender comparisons </li></ul><ul><li>e) All of these describe a randomized block design. </li></ul>
  15. 15. Experimental Design <ul><li>A randomized block design is NOT </li></ul><ul><li>d) only used for gender comparisons </li></ul>
  16. 16. Experimental Design <ul><li>A medical researcher is interested in testing a new </li></ul><ul><li>medicine for migraine headaches. She decides to </li></ul><ul><li>conduct a clinical trial on 100 randomly selected </li></ul><ul><li>adults who get migraine headaches at a rate of one </li></ul><ul><li>per week or more. Although age and gender are not </li></ul><ul><li>of primary interest in the trials, the researcher is </li></ul><ul><li>concerned that these factors may impact the </li></ul><ul><li>effectiveness of the drug. </li></ul><ul><li>  </li></ul><ul><li>Describe how she should set up her experiment for </li></ul><ul><li>the 100 subjects without considerations of age and </li></ul><ul><li>gender. A graphic is an acceptable answer. </li></ul>
  17. 17. Experimental Design <ul><li>  </li></ul><ul><li>Describe how she should set up her experiment for </li></ul><ul><li>the 100 subjects without considerations of age and </li></ul><ul><li>gender. A graphic is an acceptable answer. </li></ul>Randomize 50 adults new drug 50 adults old drug Measure and compare number of headaches
  18. 18. Experimental Design <ul><li>A medical researcher is interested in testing a new </li></ul><ul><li>medicine for migraine headaches. She decides to </li></ul><ul><li>conduct a clinical trial on 100 randomly selected </li></ul><ul><li>adults who get migraine headaches at a rate of one </li></ul><ul><li>per week or more. Although age and gender are not </li></ul><ul><li>of primary interest in the trials, the researcher is </li></ul><ul><li>concerned that these factors may impact the </li></ul><ul><li>effectiveness of the drug. </li></ul><ul><li>  </li></ul><ul><li>Describe how she should set up her experiment for the 100 </li></ul><ul><li>subjects if she wishes to control for gender. </li></ul><ul><li>  </li></ul>
  19. 19. Experimental Design <ul><li>Describe how she should set up her experiment for </li></ul><ul><li>the 100 subjects if she wishes to control for gender. </li></ul><ul><li>-It is believed that males and females will respond differently to the drug, so we block by gender. </li></ul>Male Female New drug Old drug New drug New drug Measure number of headaches & compare Measure number of headaches & compare
  20. 20. Barron’s Problems <ul><li>P. 369 #12, 18, 25, 33, 34 </li></ul><ul><li>P. 377 #3 </li></ul><ul><li>P. 430 #1 </li></ul>

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