1. CLD9003 Statistics in Modern Society
Alan Lam
Dept of CDS

2. CLD9003 Statistics in Modern Society
Course Outline
A General Education course
Sectional Approach
Class discussion (Major Emphasis)
Course text
Bennett, J.O., Briggs, W.L. and Triola, Mario F Statistical Reasoning for Everyday Life, 4/E, Addison-Wesley.
CLD9003 Statistics in Modern Society

3. CLD9003 Statistics in Modern Society
Course Outline
Tentative Schedule
Software
Excel/SPSS
Assessment
Attendance 5%
Group Project 20%
Participation 15%
Examination 60%
CLD9003 Statistics in Modern Society

4. What Is/Are Statistics
Two Definitions
Statistics is the science of collecting, organising, and interpreting data.
Statistics are the data that describe or summarize something.
GED111/CDS111 Statistics in Modern Society

5. GED111/CDS111 Statistics in Modern Society
How does it work?
Advertising
Claim of million watched a TV program
Survey of 5000 homes
Goal – population
The population in a statistical study is the complete set of people or things being studied.
Population parameters
Specific characteristics of the population
Mean, median, mode, standard deviation, size, etc.
GED111/CDS111 Statistics in Modern Society

6. What actually gets studied?
Sample
A subset of the population from which data are actually obtained
Sample statistics
Characteristics of the sample found by consolidating or summarizing the raw data
Mean, median, mode, standard deviation, size, etc.
Raw data
The actual measurements or observations collected
CLD9003 Statistics in Modern Society

7. How do sample statistics relate to population parameters?
Estimation / Inferential statistics
Margin of error
The sample represents the population fairly
The margin of error is generally smaller for a larger sample
10% for sample size of 100
5% for sample size of 400
3% for sample size of 1,000
1 % for sample 10,000
GED111/CDS111 Statistics in Modern Society

8. GED111/CDS111 Statistics in Modern Society
Margin of Error
Used to describe the range of values likely to contain the population parameter.
The range is found by sample ± margin of error
From (sample statistic – margin of error) to (sample statistic + margin of error)
GED111/CDS111 Statistics in Modern Society

9. The Process of a Statistical Study
Start
1 Identify goals
2 Draw from population
Population
Sample
3 Collect raw data and summarize
5 Draw conclusions
Population Parameters
Sample Statistics
4 Make inferences about population(estimation)
GED111/CDS111 Statistics in Modern Society

10. Decisions for an Uncertain World
Decision making under uncertainty
Ad hoc case with no historical record
One off decision making
GED111/CDS111 Statistics in Modern Society

11. GED111/CDS111 Statistics in Modern Society
Exercises
11. Stem Cell Research p.9
13. Galactic Distances p.9
21. Do People Lie About Voting? P.10
Exercise
24, 25, 26 (p.10)
GED111/CDS111 Statistics in Modern Society

12. GED111/CDS111 Statistics in Modern Society
Sampling
Census
The collection of data from every member of a population
Sampling
Collection of data from part of the population
Representative Sample
The relevant characteristics of the sample members are generally the same as the characteristics of the population
Bias
If a statistical study’s design or conduct tends to favour certain results
GED111/CDS111 Statistics in Modern Society

13. GED111/CDS111 Statistics in Modern Society
Sampling Methods
Simple Random Samples
Assign number to every possible outcome and each outcome is equally likely to be selected
Systematic Sampling
Selection made every nth possible outcomes
Convenience Samples
Based on the convenience of selection
More prone to bias than most other forms of sampling
GED111/CDS111 Statistics in Modern Society

14. GED111/CDS111 Statistics in Modern Society
Sampling Methods
Cluster Samples
Selection of all members in randomly selected groups
Stratified Samples
Population is divided into strata (subgroup)
Selection is made from each stratum and combined to form the sample
GED111/CDS111 Statistics in Modern Society

15. Summary of Sampling Methods
Regardless of how a sample is chosen, the study can be successful only if the sample is representative of the population
A biased sample is very unlikely to be a representative sample
A well-chosen sample has a good chance of being representative, but still may turn out to be biased just because of bad luck in the actual drawing of the sample
GED111/CDS111 Statistics in Modern Society

16. GED111/CDS111 Statistics in Modern Society
Exercises
Census or not
7. You want to determine the mean GPA of the 50 students in a particular high school Maths class
8. You want to determine the mean GPA of all high school senior in USA
9. You want to determine the mean annual energy costs of all homes in Missouri
10. You want to determine the mean temperature of coffee server at Starbucks
GED111/CDS111 Statistics in Modern Society

17. GED111/CDS111 Statistics in Modern Society
Exercises
Identifying the Sampling Methods p.19
23-32
Choosing a Sampling Methods p.20
39-42
GED111/CDS111 Statistics in Modern Society

18. Types of Statistical Studies
Observational Study
Observe or measure characteristics of the subjects, but do not attempt to influence or modify these characteristics
Experiment
Apply some treatment and observe its effects on the subject of the experiment
Meta-analysis
Study a topic that has been the subject of many previous studies
GED111/CDS111 Statistics in Modern Society

19. Observational Study : Retrospective Studies (Case-Control Study)
A retrospective study is an observational study that resembles an experiment because the sample naturally divides into two (or more) groups. The participants who engage in the behaviour under study form the cases, like a treatment group in an experiment. The participants who do not engage in the behaviour are the controls, like a control group in an experiment.
Usually uses data from the past, such as official records or past interviews.
GED111/CDS111 Statistics in Modern Society

20. Observational Study : Prospective Studies (Longitudinal study)
Designed to collect observations in the future from groups that share common factors
CLD9003 Statistics in Modern Society

21. Experiment : Treatment & Control Groups
Treatment group
The group of subjects who receive the treatment being tested
Control group
The group of subjects who do not received the treatment being tested.
To assign treatment & control groups
Randomisation
Large number of subjects
GED111/CDS111 Statistics in Modern Society

22. GED111/CDS111 Statistics in Modern Society
Confounding Factor
The effect of different factors are mixed so that we cannot determine the effects of the specific factors we are studying.
The factors that lead to the confusion are called confounding factors.
GED111/CDS111 Statistics in Modern Society

23. GED111/CDS111 Statistics in Modern Society
Placebo Effect
It refers to the situation in which patients improve simply because they are receiving a useful treatment
A placebo lacks the active ingredients of a treatment being tested in a study, but is identical in appearance to the treatment. Thus, study participants cannot distinguish the placebo from the real treatment.
GED111/CDS111 Statistics in Modern Society

24. GED111/CDS111 Statistics in Modern Society
Experimenter Effects
Occurs when a research or experimenter somehow influences subjects through such factors as facial expression, tone of voice, attitude.
Blinding
Single-blind
Double-blind
GED111/CDS111 Statistics in Modern Society

25. GED111/CDS111 Statistics in Modern Society
Exercises
Observational – case-control study?
Experiment – treatment/control groups?
Meta-analysis
Ex 10, 12, 13, 14 (p.32)
Anything wrong?
Ex 21, 22, 24, 25, 27 (p.32)
GED111/CDS111 Statistics in Modern Society

26. Should you believe a Statistical Study?
Eight Guidelines for Critically Evaluating a Statistical Study
GED111/CDS111 Statistics in Modern Society

27. GED111/CDS111 Statistics in Modern Society
The guidelines
1. Get a big picture view of the study
What was the study designed to determine?
The population?
Observation, experiment, meta-analysis?
GED111/CDS111 Statistics in Modern Society

28. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
2. Consider the source, particularly with regard to whether the researchers may be biased
Peer review
Several experts in a field evaluate a research report before the report is published
Published journal
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29. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
3. Look for Bias in the sample
Selection bias
Participation bias
Self-selected surveys/voluntary response surveys
GED111/CDS111 Statistics in Modern Society

30. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
4. Look for problems in defining or measuring the variables of interest, which can make it difficult to interpret any reported results.
Variable is any item or quantity that can vary or take on different values
Variables of interest in a statistical study are the items or quantities that the study seeks to measure
GED111/CDS111 Statistics in Modern Society

31. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
5. Watch out for confounding variables that can invalidate the conclusions of a study
GED111/CDS111 Statistics in Modern Society

32. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
6. Consider the setting and wording of any survey, looking for anything that might tend to produce inaccurate or dishonest responses.
Badly worded survey
Sensitive information
GED111/CDS111 Statistics in Modern Society

33. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
7. Check that results are fairly represented in graphics and concluding statements, because both researchers and media often create misleading graphics or jump to conclusions that the results do not support.
Personal bias
Unwarranted conclusions
GED111/CDS111 Statistics in Modern Society

34. GED111/CDS111 Statistics in Modern Society
The guidelines (cont.)
8. Stand back and consider the conclusions.
Did the study achieve its goal?
Do the conclusions make sense?
Can you rule out alternative explanations for the results?
If the conclusions make sense, do they have any practical significance?
GED111/CDS111 Statistics in Modern Society

35. CLD9003 Statistics in Modern Society
Focus on Sociology
Does Daycare Breed Bullies pp45-48
CLD9003 Statistics in Modern Society