Chapter 11 Where Do Data Come From?

Chapter 12 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 13 Thought Question 2 It is popular knowledge that for similar jobs men earn more money on average than women, and yet there are cases where some women make more money than some men. Therefore, to determine if men really do earn more, you would need to sample many people of each sex. Suppose we also want to know if, on average, men stay at their current jobs for a longer time period than women. How could you go about trying to determine this? Would it be sufficient to collect data for one member of each sex?... two members of each sex? What information about men’s and women’s measurements would help you decide how many people to measure?

Chapter 14 Thought Question 3 In 1997, the Orlando Sentinel released the results of a poll in which more than 90 percent 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 15 What is STATISTICS ? u Using ‘data’ to draw a conclusion about something unknown. u Decision making in the presence of uncertainty.

Chapter 16 What Is “Data”? (better: What are data?) u Pieces of information. u Numbers. u The above are data only if the information has a meaning attached.

Chapter 17 How Data are Obtained u Observational Study –Observes individuals and measures variables of interest but does not attempt to influence the responses –Describes some group or situation –Sample Surveys are a type of observational study u Experiment –Deliberately imposes some treatment on individuals in order to observe their responses –Studies whether the treatment causes change in the response.

Chapter 18 Common Language u Individuals u Population –entire group of individuals about which we want information u Sampling Frame –individuals that could possibly be selected for the sample (not necessarily the same as the population) u Sample –subset of individuals from which information is collected u Sample Survey –type of observational study; data collected on a sample u Census u Variable –characteristic of an individual

Chapter 19 Population individuals

Chapter 110 Sampling Frame List of Individuals Sample

Chapter 111 Sample Survey measurements data

Chapter 112 List of Individuals Census Census

Chapter 113 Case Study The Effect of Hypnosis on the Immune System reported in Science News, Sept. 4, 1993, p. 153

Chapter 114 Case Study The Effect of Hypnosis on the Immune System Objective: To determine if hypnosis strengthens the disease-fighting capacity of immune cells.

Chapter 115 Case Study u 65 college students. –33 easily hypnotized –32 not easily hypnotized u white blood cell counts measured u all students viewed a brief video about the immune system.

Chapter 116 Case Study u Students randomly assigned to one of three conditions –subjects hypnotized, given mental exercise –subjects relaxed in sensory deprivation tank –control group (no treatment)

Chapter 117 Case Study u white blood cell counts re-measured after one week u the two white blood cell counts are compared for each group u results –hypnotized group showed larger jump in white blood cells –“easily hypnotized” group showed largest immune enhancement

Chapter 118 Case Study The Effect of Hypnosis on the Immune System What is the population? What is the sample?

Chapter 119 Case Study The Effect of Hypnosis on the Immune System What data were collected? u Easy or difficult to achieve hypnotic trance u Group assignment u Pre-study white blood cell count u Post-study white blood cell count

Chapter 120 Case Study The Effect of Hypnosis on the Immune System Is this an experiment or an observational study?

Chapter 121 Case Study The Effect of Hypnosis on the Immune System Does hypnosis and mental exercise affect the immune system?

Chapter 122 Case Study Weight Gain Spells Heart Risk for Women “Weight, weight change, and coronary heart disease in women.” W.C. Willett, et. al., vol. 273(6), Journal of the American Medical Association, Feb. 8, (Reported in Science News, Feb. 18, 1995, p. 108)

Chapter 123 Case Study Weight Gain Spells Heart Risk for Women Objective: To recommend a range of body mass index (a function of weight and height) in terms of coronary heart disease (CHD) risk in women.

Chapter 124 Case Study u Study started in 1976 with 115,818 women aged 30 to 55 years and without a history of previous CHD. u Each woman’s weight (body mass) was determined u Each woman was asked her weight at age 18.

Chapter 125 Case Study u The cohort of women were followed for 14 years. u The number of CHD (fatal and nonfatal) cases were counted (1292 cases). u Results were adjusted for other variables.

Chapter 126 Case Study u Results: compare those who gained less than 11 pounds (from age 18 to current age) to the others. –11 to 17 lbs: 25% more likely to develop heart disease –17 to 24 lbs: 64% more likely –24 to 44 lbs: 92% more likely –more than 44 lbs: 165% more likely

Chapter 127 Case Study Weight Gain Spells Heart Risk for Women What is the population? What is the sample?

Chapter 128 Case Study Weight Gain Spells Heart Risk for Women What data were collected? u Age (in 1976) u Weight in 1976 u Weight at age 18 u Incidence of coronary heart disease u Other: smoking, family history, menopausal status, post-menopausal hormone use.

Chapter 129 Case Study Weight Gain Spells Heart Risk for Women Is this an experiment or an observational study?

Chapter 130 Case Study Weight Gain Spells Heart Risk for Women Does weight gain in women increase their risk for CHD?

Chapter 131 Key Concepts u Knowing about statistical methods will have practical consequences in your every day lives. u Experiment versus Observational Study u Common Terms –Individuals, Population, Sampling Frame, Sample, Sample Survey, Census, Variable