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Chapter 5

Chapter 5. The entire group of individuals about which we want information. A part of the population from which we actually collect data. Collecting data from every member of a population. Collecting data from a part of population to gain information about the whole population.

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Chapter 5

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  1. Chapter 5

  2. The entire group of individuals about which we want information A part of the population from which we actually collect data Collecting data from every member of a population Collecting data from a part of population to gain information about the whole population

  3. All adult US residents 1500 adults who respond

  4. Convenience sample Voluntary response sample Choosing individuals who are easiest to reach

  5. over- or underestimates Students in the library probably study more than average students

  6. People who choose themselves by responding to a general request

  7. People who are strongly opposed to illegal immigration are most likely to respond.

  8. Choose a sample by chance Don’t allow for favoritism by sampler or respondents

  9. Assign Table B stop sampling identify your sample Each label must have the same number of digits! EX: 01 to 50, not 1 to 50

  10. 01 08 15 02 09 16 03 10 17 04 11 18 05 12 19 06 13 20 07 14 21

  11. Alphabetize stores Assign a number 001 to 440 to each store Use a table of random digits to choose groups of 3 digits until sample of 10 is obtained. Ignore repeats 400, 077, 172, 417, 350, 131, 211, 273, 208, 074

  12. Stratified random sample Cluster sample Systematic sample Multistage sample

  13. strata sample combined

  14. clusters sample

  15. seminars 9th 01 02 03 04 SRS of 30 10th SRS of 30 05 06 07 08 11th SRS of 30 09 10 11 12 12th 13 14 15 16 SRS of 30

  16. Number each student 0001 0002 0003 0004 ….. 0011 0012 0013 0014 ….. 0021 0022 0023 0024 ….. 2400/120 = 20 Take every 20th student

  17. Cluster sampling Stratified sampling Convenience sampling

  18. SRS Systematic sampling Multi-stage sampling

  19. Homework #1, 3, 5, 6, 11, 14, 18

  20. Undercoverage Nonresponse Response bias

  21. left out Leaves out college students, active military, homeless Leaves out anyone without a land-line phone

  22. refuse to participate

  23. respondent interviewer Might lie if asked about unpopular or illegal behavior Might guess if they don’t understand the question Inaccuracies due to faulty memory Race, gender, appearance or attitude of interviewer may influence responses.

  24. leading Implies that status quo is unfair to non-smokers Probably influence more people to say “yes” States that taxes are unfair to smokers Probably influence more people to say “no”

  25. More important to explain the error in sampling than to use the correct vocab (undercoverage vs. nonresponse)

  26. Homework #10, 19, 20, 22, 23

  27. Researchers observe individuals to measure variables, but do not attempt to influence the responses.

  28. Researchers deliberately do something to individuals in order to measure their responses.

  29. People, animals or objects on which the experiment is performed. Experimental units that are humans. Specific condition applied to the individuals Explanatory variable(s) in the experiment Specific values for each factor

  30. Paper helicopters 2 Rotor length: 2 levels (long and short) Drop height: 3 levels (low, medium, high)

  31. 6 treatments long rotor, low drop height short rotor, low drop height long rotor, med drop height short rotor, med drop height long rotor, high drop height short rotor, high drop height Distance from target

  32. Tomato plants 2 Fertilizer: 2 levels (yes or no) Water: 4 levels (0.5, 1, 1.5, 2 gal)

  33. 8 treatments No fertilizer, 0.5 gal Fertilizer, 0.5 gal No fertilizer, 1 gal Fertilizer, 1 gal No fertilizer, 1.5 gal Fertilizer, 1.5 gal No fertilizer, 2 gal Fertilizer, 2 gal Weight of tomatoes produced by the plant

  34. Experimental units are assigned to treatments at random. Write each name on a piece of paper First 25 picked go to the “online” group. OR write “online” or “classroom” on 25 slips each. Every student draws one.

  35. Assign each student a number, 01 to 50 Go to a line in rand digit table and read 2-digit groups. First 25 selected go to online group

  36. Group 1 25 students Treatment 1 Online course 50 volunteers Random Assignment Compare ACT score Treatment 2 Classroom course Group 2 25 students

  37. Homework Problems #26, 28, 31, 37, 46, 48, 50

  38. cause equally lurking variables similar treatment

  39. Group that doesn’t receive the treatment being examined Provides a baseline for comparing effects of other treatments

  40. CONTROL RANDOMIZATION REPLICATION

  41. An observed effect is so large, it would rarely occur by chance Means it is likely the treatment caused those differences

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