CLD9003 Statistics in Modern Society

1. CLD9003Statistics in Modern Society Alan Lam Dept of CDS

2. Course Outline • A General Education course • Sectional Approach • Class discussion (Major Emphasis) • Course text • Bennett, J.O., Briggs, W.L. and Triola, Mario F. 2014 Statistical Reasoning for Everyday Life, 4/E, Addison-Wesley. CLD9003 Statistics in Modern Society

3. 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. How does it work? • Advertising • Claim of 111.3 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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 GED111/CDS111 Statistics in Modern Society

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

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