BUS 418 CHAPTER 16 SAMPLING DESIGNS AND SAMPLING

BUS 418: CHAPTER 16 SAMPLING DESIGNS AND SAMPLING PROCEDURES Introduction Sampling Terminology • A sample is a subset, or some part, of a larger population. The purpose of sampling is to estimate an unknown characteristic of a population. • A population (universe) is any complete group—for example, of people, sales territories, stores, or college students—that shares some common set of characteristics. • The term population element refers to an individual member of the population. Why Sample? • Pragmatic Reasons Impossible to contact all • Accurate and Reliable Results • Destruction of Test Units

Practical Sampling Concepts Defining the Target Population The Sampling Frame • A list of elements from which the sample may be drawn • A sampling frame error occurs when certain sample elements are excluded or when the entire population is not accurately represented in the sampling frame. Sampling Units • The sampling unit is a single element or group of elements subject to selection in the sample. For example, if an airline wishes to sample passengers, it may take every 25 th name • on a complete list of passengers. In this case the sampling unit would be the same as the element. • A unit selected in the first stage of sampling is called a primary sampling unit (PSU). • A unit selected in a successive stages of sampling is called a secondary sampling unit or • (if three stages are necessary) tertiary sampling unit.

Random Sampling and Nonsampling Errors Random sampling error is the difference between the sample result and the result of a census conducted using identical procedures. Systematic Sampling Error Systematic (nonsampling) errors result from nonsampling factors, primarily the nature of a study’s design and the correctness of execution. These errors are not due to chance fluctuations. For example, highly educated respondents are more likely to cooperate with mail surveys than poorly educated ones, for whom filling out forms is more difficult and intimidating. • Less than Perfectly Representative Samples • Random sampling errors and systematic errors associated with the sampling process may combine to yield a sample that is less than perfectly representative of the population. Probability versus Nonprobability Sampling • Convenience Sampling • Judgment Sampling • Quota Sampling • Snowball Sampling Probability Sampling • Simple Random Sampling • Systematic Sampling • Stratified Sampling

Proportional versus Disproportional Sampling Cluster Sampling Multistage Area Sampling • Multistage area sampling involves two or more steps that combine some of the probability techniques already described. Typically, geographic areas are randomly selected in progressively smaller (lower-population) units. • For example, a political pollster investigating an election in Arizona might first choose counties within the state to ensure that the different areas are represented in the sample. What Is the Appropriate Sample Design? • Degree of Accuracy • Resources • Time • Advance Knowledge of the Population

Internet Sampling Is Unique • Web Site Visitors • Panel Samples Drawing a probability sample from an established consumer panel or other prerecruited membership panel is a popular, scientific, and effective method for creating a sample of Internet users. • Recruited Ad Hoc Samples Researchers may create the sampling frame offline or online. Databases containing email addresses can be compiled from many sources, including customer/client lists, advertising banners on pop-up windows that recruit survey participants, online sweepstakes, and registration forms that must be filled out in order to gain access to a particular • Opt-in Lists The company offers more than 3, 500 lists of high-quality, targeted e-mail addresses of individuals who have given permission to receive e-mail messages related to a particular topic of interest. Survey Sampling International’s database contains millions of Internet users who opt in for limited participation. An important feature of Survey Sampling International’s database is that the company has each individual confirm and reconfirm interest in communicating about a topic before the person’s e-mail address is added to the company’s database.