C H A P T E R 15 Taking short cuts – sampling methods Chapter objectives This chapter will help you to: ■ ■ ■ appreciate the reasons for sampling understand sampling bias and how to avoid it employ probabilistic sampling methods and be aware of their limitations ■ use the technology: simple random sampling in MINITAB and SPSS ■ become acquainted with business uses of sampling methods | CHAPTER 15 Taking short cuts -sampling methods Chapter objectives This chapter will help you to appreciate the reasons for sampling understand sampling bias and how to avoid it employ probabilistic sampling methods and be aware of their limitations use the technology simple random sampling in MINITAB and SPSS become acquainted with business uses of sampling methods A population is the entire set of items or people that form the subjects of study in an investigation and a sample is a subset of a population. Companies need to know about the populations they deal with populations of customers employees suppliers products and so on. Typically these populations are very large so large that they are to all intents and purposes infinite. Gathering data about such large populations is likely to be very expensive time-consuming and to a certain extent impractical. The scale of expense can be immense even governments of large countries only commit resources to survey their entire populations that is to conduct a census about every ten years. The amount of time involved in surveying the whole population means that it may be so long before the results are available that they are completely out of date. There may be some elements within the Chapter 15 Taking short cuts - sampling methods 467 population that simply cannot be included in a survey of it for instance a car manufacturer may want to conduct a survey of all customers buying a certain model three years before in order to gauge customer satisfaction. Inevitably a number of those customers will have died in the period since buying their car and thus cannot be included in the survey. To satisfy their need for data about the populations that matter to them without having to incur great expense or wait a long time for results companies turn to sampling the process of taking a sample from a population in order to use the sample data to gain insight into the entire population. Although not as accurate as the results of a .
