1. Vocabulary of Statistics
Part 3

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

3. Other methods of data collection
Observation
direct
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: 600 kids at CHS. We want a sample of 100.
600 ÷ 100 = Interview every 6th 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 Chatham 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. What ‘ s the Problem Each of the following graphs is faulty!!
Find the errors!
Write some about the problem and how it can be fixed!

23. Misleading Graphs

26. 51% agree
49% disagree

27. 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?

28. 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.

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

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