1. Survey Research & Understanding Statistics

2. Central Tendency

3. Measures of Central Tendency
Average (Mean)
Median
Mode

4. Mean (Arithmetic Mean)
Mean (arithmetic mean) of data values
Sample mean
Sample Size

5. Mean The most common measure of central tendency
Affected by extreme values (outliers)
Mean = 5
Mean = 6

6. Median Robust measure of central tendency
Not affected by extreme values
Median is the “middle” number
Median = 5
Median = 5

7. Mode A measure of central tendency Value that occurs most often
Not affected by extreme values
Used for either numerical or categorical data
There may may be no mode
There may be several modes
No Mode
Mode = 9

8. Survey Research

9. What is a Survey?
Researchers are often interested in the opinions of a large group of people about a particular topic or issue.
There are three major characteristics that most surveys possess:
Information is collected from a group of people in order to describe some aspect of the population
Information is collected by asking questions of the members of the selected group
Information is collected from a sample rather than from every member of the population

10. Question
What are common problems with survey research?

11. Why Are Surveys Conducted?
The purpose of surveys is to describe the characteristics of a population.
Researchers find out how the members of a population distribute themselves on one or more variables.
A selected sample is surveyed and the description of the population is inferred from what is found out about the sample.
In descriptive surveys, researchers are not as concerned about why the observed distribution exists as with what the distribution is.

12. Types of Surveys There are two types of surveys:
Cross-sectional survey
Collects information from a sample that has been drawn from a predetermined population
Information is collected at just one point in time, even though it could take days to gather all the data
A census is when the entire population is surveyed
Longitudinal survey
Information is collected at different points in time in order to study changes over time
Three types are employed:
Trend study
Cohort Study
Panel Study

13. Survey Research and Correlational Research
Techniques of Correlational Research can be tied in with Survey Research.
Researchers could look at the relationship of responses to one question (survey) to another, or of a score based on one set of questions to another set.
The use of calculating correlation coefficients or contingency tables could be determined and implemented.

14. Steps in Survey Research
The following steps are used in conjunction with performing proper surveys in research:
Defining the problem
Identifying the target population (unit of analysis)
Choosing the mode of data collection
Direct administration
Mail surveys
Telephone surveys
Personal interviews

15. Example of an Ideal vs. an Actual Telephone Sample for a Specific Question

16. Steps in Survey Research (cont.)
The following steps are used in conjunction with performing proper surveys in research:
Selecting the sample
Preparing the instrument (questionnaire)
Closed-ended questions
Open-ended questions
Pre-testing the questionnaire
Format
Cover letter
Training interviewers

18. Example of Contingency Questions

19. Non-response
In almost all surveys, some members of the sample will not respond.
Item non-response is due to unclear or questionable forms of wording.
Non-response is a serious problem in many surveys.
A variety of techniques are employed to reduce this problem (e.g., rewards or incentive for completing the surveys).

20. Data Analysis in Survey Research
After researchers receive the completed questionnaires, the task of summarizing the results remains.
The total size of the sample and total percentage of returns should be reported.
The percentage of the total sample responding for each item should be reported.
The percentage of respondents who chose each alternative for each question should be given.

21. Variability

22. Shapes of Distributions
Normal distribution
Positive Skew
Or right skewed
Negative Skew
Or left skewed

23. How is this variable distributed?

24. How is this variable distributed?

25. How is this variable distributed?

26. Standard Deviation Considered the most useful index of variability.
It is a single number that represents the spread of a distribution.
If a distribution is normal, then the mean plus or minus 3 SD will encompass about 99% of all scores in the distribution.

27. Comparing Standard Deviations
Data A
Mean = 15.5
S = 3.338
Data B
Mean = 15.5
S = .9258
Data C
Mean = 15.5
S = 4.57

28. Facts about the Normal Distribution
50% of all the observations fall on each side of the mean.
68% of scores fall within 1 SD of the mean in a normal distribution.
27% of the observations fall between 1 and 2 SD from the mean.
99.7% of all scores fall within 3 SD of the mean.
This is often referred to as the rule

29. Fifty Percent of All Scores in a Normal Curve Fall on Each Side of the Mean

30. Probabilities Under the Normal Curve

31. The Importance of Converging Evidence
The connectivity principle
New theory in science must make contact with established facts.
Beware of violations of connectivity.
Converging evidence
Single studies have flaws
Together the flaws should wash out.
When might this not be true?

32. Meta-Analysis
A meta-analysis is a statistical procedure when the researcher averages the results of a group of selected studies to get an overall index of outcome or relationship.

33. Experimental vs. Nonexperimental
Experiments
Treatment is administered
Students divided into two groups; one group receives new reading materials the other uses the traditional materials.
Cancer patients are divided into two groups; one group receives a new drug the other receives the current treatment of choice.
Nonexperiments
No manipulation of treatment present
Individuals given a survey asking about television viewing habits.
Classrooms observed to see if teacher’s expectations affect student performance.

34. Correlational Study Relationships SAT and Achievement
Income and achievement
Age and Cholesterol level

35. Causal-Comparative Studies.
Causal-comparative (a.k.a. ex post facto)
Two characteristics
Observe and describe a current condition
Look to the past, or demographic characteristics, to identify a cause.

36. Survey Research Used to describe Usually include large numbers
Attitudes
Opinions
Beliefs
Behaviors
Usually include large numbers