1. Vocabulary of Statistics Part 3

2. Data Collection - Surveys  Telephone pros: less costly, more candid pros: less costly, more candid cons: no phone, no call list cons: no phone, no call list  Mailed questionnaire pros: cover more area, less cost pros: cover more area, less cost cons: low response, inappropriate responses cons: low response, inappropriate responses  Personal Interview pros: in-depth responses, pros: in-depth responses, cons: training, cost, bias cons: training, cost, bias

3. Other methods of data collection  Observation direct indirect indirect  surveying records

4. Four Methods of Sampling  Random  Systematic  Stratified  Cluster

5. Random  selected by using chance methods or random numbers  put everybody’s name in a bucket and choose  assign a number, use a random number generator

6. Systematic  Number each subject of the population, then select every nth subject. example: 1600 kids at MHS. We want a sample of 200. 1600 ÷ 200 = 8 Interview every 8 th kid.

7. Stratified  Divide the population into groups (called strata) according to some characteristic that is important to the study. example: you might want to only survey juniors.

8. Cluster  Use an entire, intact, group. example: every person who lives in a certain apartment building. example: every person in Mrs. Peddy’s third period class.

9. These are not the only methods  convenience sampling - whatever is convenient to the researcher (Wal-mart)  sequential  double sampling  multi-stage

10. Observational Studies  The researcher merely observes what is happening or what has happened in the past and tries to draw conclusions based on these observations.

11. Experimental Study  The researcher manipulates one of the variables and tries to determine how the manipulation influences other variables. teaching note: situps

12.  In a true experimental study, subjects should be assigned randomly  when random assignment is not possible (i.e. existing classrooms), the study is said to be quasi- experimental

13. Independent Variable  The variable that is being manipulated  aka: explanatory variable

14. Dependent Variable  The resultant variable.  aka: outcome variable.

15. When doing an experiment you generally need two groups: treatment group: the one you are experimenting on control group: the one you are doing nothing to but observing

16. Confounding Variable  a variable that influences the dependent or outcome variable but cannot by separated from the independent variable.

17. Misuse of Statistics

18.  3% of the students of Muskogee High School want school uniforms.  64% of the students of Muskogee High School want school uniforms. Which one is true?

19.   The pure and simple truth is rarely pure and never simple Oscar Wilde   First get your facts; then you can distort them at your leisure Mark Twain   There are three kinds of lies: lies, damn lies, and statistics Benjamin Disraeli

20. Three out of four doctors recommend new Zimento

21. Suspect Samples  How many doctors were actually used?  4?  40?  100?  10,000?  How were they chosen?

22. Misleading Graphs

25. 51% agree 49% disagree

26. Misleading wording in surveys  Do you support bringing freedom and democracy to the people of Iraq?  Do you support the unprovoked military action of the U.S. taking place in Iraq?

27. Changing values to represent the same data  The incumbent states, “During my tenure expenditures have only risen 1%.”  The challenger states, “During my opponents tenure expenditures have risen $10,000,000.”  Both statements are true, but one uses percentage and the other dollar amounts.

28. Detached Statistics  Our brand of crackers has one-third fewer calories. compared to what?  Zimento works four times faster. faster than what?

29. Implied connections EEEEating fish may help to reduce your cholesterol. SSSStudies suggest that using Zimento will help you reduce your weight. TTTTaking calcium will lower blood pressure in some people.

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