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Understanding Data Collection Methods and Statistical Analysis

Explore the different ways data is collected, including observational studies and experiments, and learn about key statistical concepts. Evaluate the validity of study conclusions and examine practical implications in everyday life.

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Understanding Data Collection Methods and Statistical Analysis

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  1. Chapter 1 Where Do Data Come From? Chapter 1

  2. Thought Question 1 From a recent study, researchers concluded that high levels of alcohol consumption resulted in lower graduation rates at colleges. How do you think this study was carried out in order to get these results? Do you think the conclusion is correct? Is there a more reasonable conclusion? Chapter 1

  3. Thought Question 2 In 1997, the Orlando Sentinel released the results of a poll in which more than 90% of those people who called in to the paper said that Orlando’s NBA team, the Orlando Magic, should not re-sign its center, Shaquille O'Neal, for the amount of money he was asking. Based on this poll, would you conclude that over 90% of Orlando’s population felt that the team should not re-sign Shaquille O’Neal? Chapter 1

  4. What is STATISTICS ? • There are three kinds of lies: lies, damned lies, and statistics. (Mark Twain) • Using “data” to draw a conclusion about something unknown. • Decision making in the presence of uncertainty. Chapter 1

  5. What Is “Data”?(better: What are“data”?) • Pieces of information (categorical data) • Numbers (quantitative data) • The above are data only if the information has a meaning attached. Chapter 1

  6. How Data are Obtained • Observational Study • Observes individuals and measures variables of interest but does not attempt to influence the responses • A response is a variable that measures an outcome or result of a study. • Describes some group or situation • A Sample Survey and a census are types of observational studies. • Experiment • Deliberately imposes some treatment on individuals in order to observe their responses • Studies whether the treatment causes change in the response Chapter 1

  7. Chapter 1

  8. Common Terminology • Individuals • the objects described by a set of data. Individuals may be people, animals, or things. • Population • entire group of individuals about which we want information • Sampling Frame • individuals that could possibly be selected for the sample (not necessarily the same as the population) • Sample • subset of individuals from which information is collected • Sample Survey • A kind of observational study; data collected on a sample • Census • a sample survey that attempts to include the entire population in the sample • Variable • any characteristic of an individual Chapter 1

  9. NameMajorPointsGrade Advani, Sura Math 397 B Barton, David Chem 323 C Brown, Annette Lit 446 A Chiu, Sun Psyc 405 B Cortez, Maria Psyc 461 A …. … … … Individuals are the students enrolled in the course There are three variables attached to each individual. Chapter 1

  10. individuals Population Chapter 1

  11. 3 4 5  6 2 1 7 10 11 8 12 9   13 15 17 14 16  Sample  List of Individuals 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Sampling Frame Chapter 1

  12. measurements data Sample Survey Chapter 1

  13. 3 4 5  6 2  1 7 10  11 8 12  9  13 15  17 14 16    3 4 5 6  2  1 7 10 11 8  12  9 13 15  17 16 14   List of Individuals 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Census Census Chapter 1

  14. Case Study The Effect of Hypnosis on the Immune System reported in Science News, Sept. 4, 1993, p. 153 Chapter 1

  15. Case Study The Effect of Hypnosis on the Immune System Objective: To determine if hypnosis strengthens the disease-fighting capacity of immune cells. Chapter 1

  16. Case Study • 65 college students. • 33 easily hypnotized • 32 not easily hypnotized • White blood cell counts measured • All students viewed a brief video about the immune system. Chapter 1

  17. Case Study • Students randomly assigned to one of three conditions • subjects hypnotized, given mental exercise • subjects relaxed in sensory deprivation tank • control group (no treatment) Chapter 1

  18. Case Study • White blood cell counts re-measured after one week. • The two white blood cell counts were compared for each group. • Results: • The hypnotized group showed larger jump in white blood cells. • The “easily hypnotized” group showed the largest immune enhancement. Chapter 1

  19. Case Study The Effect of Hypnosis on the Immune System What is the population? What is the sample? Chapter 1

  20. Case Study • Easy or difficult to achieve hypnotic trance • Group assignment • Pre-study white blood cell count • Post-study white blood cell count The Effect of Hypnosis on the Immune System What data were collected? Chapter 1

  21. Case Study The Effect of Hypnosis on the Immune System Is this an experiment or an observational study? Chapter 1

  22. Case Study The Effect of Hypnosis on the Immune System Do hypnosis and mental exercise affect the immune system? Chapter 1

  23. Key Concepts • Knowing about statistical methods will have practical consequences in your everyday lives. • Experiment versus Observational Study • Common Terms • Individuals, Population, Sampling Frame, Sample, Sample Survey, Census, Variable Chapter 1

  24. Exercise A press release by the Gallup News Service says that it found “75% of Americans saying the entertainment industry should make a serious effort to reduce the amount of sex and violence in its movies, TV shows, and music ”. Toward the end of the article, you read: “These polls are based on telephone interviews with a randomly selected national sample of 1008 adults.” What variable did this poll measure? What population do you think Gallup wants information about? What was the sample? Chapter 1

  25. Exercise 1.10 • For each of the following sampling situations, identify the population as exactly as possible. • A Sociologist is interested in determining the extent to which teens are self-motivated. She selects a sample of four high schools in a large city and interviews all tenth-graders in each of the schools. • The lecturer in a large introductory mathematics course is concerned about the accuracy with which multiple-choice tests are graded by her teaching assistants. After the most recent test, she selects a sample of the exams and regrades them. • The host of a local radio talk show wonders if people who are actively religious are happier than those who are not. The station receives calls from 48 listeners who voice their opinions. Chapter 1

  26. Exercise 1.15 • A study of the relationship between physical fitness and leadership uses as subjects middle-aged executives who have volunteered for an exercise program. The executives are divided into a low-fitness group and a high-fitness group on the basis of a physical examination. All subjects then take a psychological test designed to measure leadership, and the results for the two groups are compared. Is this an experiment, a sample survey, or an observational study that is not a sample survey? Chapter 1

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