统计学CH05 英文版.ppt

Keller: Stats for Mgmt Econ, 7th Ed Copyright ? 2006 Brooks/Cole, a division of Thomson Learning, Inc. Chapter Five Data Collection and Sampling Recall… Statistics is a tool for converting data into information: Methods of Collecting Data… There are many methods used to collect or obtain data for statistical analysis. Three of the most popular methods are: ? Direct observation (E.g. Number of customers entering a bank per hour) ??Experiments (E.g. new ways to produce things to minimize costs) ? Surveys Surveys… A survey solicits information from people; e.g. Gallup polls; pre-election polls; marketing surveys. The Response Rate (i.e. the proportion of all people selected who complete the survey) is a key survey parameter. Surveys may be administered in a variety of ways, e.g. Personal interview, Telephone interview Self- administered questionnaire Questionnaire Design… Over the years, a lot of thought has been put into the science of the design of survey questions. Key design principles: Keep the questionnaire as short as possible. Ask short, simple, and clearly worded questions. Start with demographic questions to help respondents get started comfortably. Use dichotomous (yes|no) and multiple choice questions. Use open-ended questions cautiously. Avoid using leading-questions. Pretest a questionnaire on a small number of people. Think about the way you intend to use the collected data when preparing the questionnaire. Sampling… Recall that statistical inference permits us to draw conclusions about a population based on a sample. Sampling (i.e. selecting a sub-set of a whole population) is often done for reasons of cost (it’s less expensive to sample 1,000 television viewers than 100 million TV viewers) and practicality (e.g. performing a crash test on every automobile produced is impractical). In any case, the sampled population and the target population should be similar to one another. Sampling Plans… A sampling plan is just a method or proced