统计学的成功案例和警示故事.ppt

Statistics Success Stories and Cautionary Tales 统计学的成功案例和警示故事,LESSON 1 第一课,1.1 WHAT IS STATISTICS ? 什么是统计学,Statistics is a collection of procedures and principle for gathering data and analyzing information in order to help people make decisions when faced with uncertainty. 统计学是一套收集数据和分析信息的方法和原则，以帮助人们在面对不确定性时制定决策。,The odds of finding two identical fingerprints were 1 in 64 billion. Francis Galton,两个随机个体具有相同DNA图形的概率为310-11；如果同时用两种探针进行比较，两个个体完全相同的概率小于510-19。,每支枪的枪管都有独一无二的特征，这种特征影响了它所发射的每一发子弹。 司法弹道学,航空公司通过抽样而省钱,最早的英文原版打败庄家,1.2 SEVEN STATISTICAL STORIES WITH MORALS 7个包含寓义的统计学故事,There are three kinds of lies: lies, damned lies and statistics。 Benjamin Disraeli (British Prime Minister, 18041881),CASE STUDY 1,Who are Those Speedy Drivers? 谁是快车手？,Responses to “Whats the fastest youve ever driven?”,Dotplot,Responses to “Whats the fastest youve ever driven?”,Five-number summary,一条平均水深0.4m河流绝不会比一个平均水深0.6m的游泳池更安全,Responses to “Whats the fastest youve ever driven?”,Five-number summary,Definition: The median is the value in the middle when the numbers are put in order. The lower quartile and upper quartile are (roughly) the medians of the lower and upper halves of the data.,Moral of the story,Simple summaries of data can tell an interesting story and are easier to digest than long lists.,CASE STUDY 2,Disaster in the Skies? 空中的灾难？,“Planes get closer in midair as traffic control errors rise. Errors by air traffic controllers climbed from 746 in fiscal 1997 to 878 in fiscal 1998, an 18% increase”,-USA TODAY, Levin, 1999,“The errors per million flights handled by controllers climbed from 4.8 to 5.5” 5.54.8=114.6%,Definition: The rate is simply the number of times something occurs per number of opportunities for it to occur. Baseline rate is the rate at a beginning time period or under specific conditions.,Moral of the story,When discussing the change in the rate or risk of occurrence of something, make sure you also include the base rate or baseline risk.,CASE STUDY 3,Did anyone ask you whom youve been dating?,“According to a new USA Today/Gallup Poll of teenagers across the country, 57 percent of teens who go out on dates say theyve been out with someone of another race or ethnic group.”,-USA TODAY, Perterson, 1997,CASE STUDY 3,“In most cases, parents arent a major obstacle. Sixty-four percent of teens says their parents dont mind that they date interracially, or wouldnt mind if they did.”,-Sacramento Bee, Hiram , 1997,How could the polltakers manage to ask so many teenagers these question?,Question 1,Could such a small sample possibly tell us anything about the millions of teenagers in the United States ?,Question 2,Yes -if those teens constituted a random sample from the population of interest.,How accurate could this sample possibly be ?,Question 3,The results of this poll are accurate to within a margin of error of about 4.5% (95% confidence interval).,Moral of the story,A representative sample of only a few thousand, or perhaps even a few hundred, can give reasonably accurate information about a population of many millions.,CASE STUDY 4,Who Are Those Angry Women?,“A well-conducted survey can be very informative, but a poorly conducted one can be a complete disaster.”,-Statistics: Concepts and Controversives, David S. Moore,“The women who responded were fed up with men and eager to fight them. For example, 91% of those who were divorced said they had initiated the divorce. The anger of women toward men became the theme of the book.”,-Women and Love, Shere. Hite,Shere Hite sent questionnaires to 100,000 women asking about love, sex, and relationships.,The Hite sample exemplifies one of the most common problems with surveys-the sample data may not represent the population. Extensive nonresponse from a random sample, or the use of a self-selected (i.e., all-volunteer) sample, will probably produce biased results.,Moral of the story,An unrepresentative sample, even a large one, tell you almost nothing about the population.,Definition: Nonresponse bias can occur when many people who are selected for the sample either do not respond at all or do not respond to some of the key survey questions. This may occur even when an appropriate random sample is selected and contacted.,Magazines, television stations, and internet websites routinely conduct the survey which is based on a nonrepresentative sample, usually those who feel strongly about the issues. The sample is called a self-selected sample or a volunteer sample which tells nothing about the larger population at all, it only tells you about those who responded.,CASE STUDY 5,Does Prayer Lower Blood pressure?,Prayer Can Lower Blood Pressure “Attending religious services lowers blood pressure more than tuning into religious TV or radio, a new study says.”,-USA TODAY, Davis, 1998,People who attended a religious service once a week and prayed or studied the bible once a day were 40% less likely to have high blood pressure than those who dont go to church every week and prayed and studied the bible less.,An observational study conducted by the U.S. National Institutes of Health, which followed 2391 people aged 65 or older for six years.,Background,Criticism,Moral of the story,Cause-and-effect conclusions can not generally be made based on an observational study.,Definition: An observational study is one in which participants are merely observed and measured. A confounding variable is a variable that is not the main concern of the study, but may be partially responsible for the observed results.,CASE STUDY 6,Does Aspirin Reduce Heart Attack Rates?,Background,Time:19831988 Organizer: Steering Committee of the Physicians Health Study Research Group Objective: To determine if taking aspirin reduces the risk of a heart attack. Subject: 22,071 male physicians between the ages of 40 and 80 Method: A five-year randomized experiment,Method,2x2 factorial design,active aspirin and active beta-carotene(5,517) active aspirin and beta-carotene placebo(5,520) aspirin placebo and active beta-carotene(5,519) aspirin placebo and beta-carotene placebo(5,515),Aspirin reduced the risk of first myocardial infarction by 44% (P less than 0.00001). There were too few strokes or deaths upon which to base sound clinical judgment regarding aspirin and stroke or mortality.,Result,-New England Journal of Medicine, 1989,321(3):18-185,The Effect of Aspirin on Heart Attacks,*More than 170 other findings have emerged from the trial so far.,Moral of the story,Unlike with observational studies, cause-and effect conclusions can generally be made on the basis of randomized experiments.,Definition: A randomized experiment is a study in which treatments are randomly assigned to participants. A statistically significant relationship of difference is one that large enough to be unlikely to have occurred in the sample if there was no relationship or difference in the population.,CASE STUDY 7,Does the internet Increase Loneliness and Depression?,“greater use of the internet was associated with declines in participants communication with family members in the household, declines in size of their social circle, and increases in their depression and loneliness.”,-Internet paradox: A social technology that reduces social involvement and psychological well-being? American Psychologist, 1998,53(9):1017-1031 David S. Moore,Sad, Lonely World Discovered in Cyberspace -Amy Harmon, August 30, 1998, Sunday,Background: The study included 169 individuals in 73 households in Pittsburg, Pennsylvania who were given free computers and internet service in 1995. The participants answered a series of questions at the beginning of the study and either one or two years la