Chapter Thirteen,13-1,The entire group of people about whom information is needed; also called the universe or population of interest. The process of obtaining information from a subset of a larger group.,Sampling,Population,The Concept of Sampling,13-2,Key Terms & Definitions,Census: Data collection from or about every member of the population of interest. Also called canvassing the population by asking everyone a set of questions. Sample: A subset of all the members of a population of interest. Hopefully that subset is statistically representative of the general population.,Census vs. Sample,13-3,Key Terms & Definitions,Developing a Sampling Plan,13-4,Key Terms & Definitions,1. Define the Target Population Determine the characteristics of those you are interested in studying. Determine which group of people or entities about which you want to learn more. 2. Choose the Data Collection Method Determine how you collect the sample - such as mail, Internet, telephone, mall intercept, etc. 3. Select the Sample Frame A list of population elements from which units to be sampled can be selected.,Developing a Sampling Plan,13-5,Key Terms & Definitions,4. Select the Sampling Method Determine how you will get the sample list through probability or non-probability methods. 5. Determine the Sample Size What is the level of accuracy you want to achieve; the time and money you have to do the survey, and the data collection method? 6. Determine Operational Procedures This is the plan of how to go about actually choosing and interviewing the respondents. 7. Execute the Sampling Plan Field workers must be trained to execute the sampling plan properly.,Developing a Sampling Plan,13-6,Key Terms & Definitions,1. Defining the Population of Interest,13-7,Key Terms & Definitions,2. Choose a Data Collection Method,13-8,Key Terms & Definitions,The main methods are: Personal, such as mall intercepts, etc. Telephone Mail or other self-administered Internet, blended samples,This was discussed in the chapter on questionnaire design, also. The sample plan will depend on the data collection method, too.,3. Identify the Sampling Frame,13-9,Key Terms & Definitions,This is a list of the members or elements of the population from which units to be sampled are to be selected. There is seldom a perfect correspondence between the sample frame and the population of interest. Explain how a citys telephone book could be used as a sample frame of people in the city with telephones. What are the advantages and disadvantages of using that frame?,4. Sampling Methods,13-10,Key Terms & Definitions,A sample selected by assigning a number to every element of the population and then using some method for randomly selecting elements to be in the sample such as random digit dialing. A sample in which the entire population is numbered and elements are selected using a skip interval every “nth” name is selected.,Simple Random,Systematic,Probability Sampling,13-11,Key Terms & Definitions,A sample that is forced to be more representative through simple random sampling of mutually exclusive and exhaustive subsets either proportionally or disproportionally. Good for data that are not normally distributed. A sample in which the sampling units are selected from a number of small geographic areas to reduce data collection costs.,Cluster,Stratified,Probability Sampling,13-12,Key Terms & Definitions,Stratified Sampling Allocations,Proportional Allocation: Sampling in which the number of elements selected from a stratum is directly proportional to the size of the stratum relative to the size of the population. Disproportional, or Optimal, Allocation: Sampling in which the number of elements taken from a given stratum is proportional to the relative size of the stratum and the standard deviation of the characteristic under consideration.,13-13,Key Terms & Definitions,Multistage Sampling,Geographic areas selected for national or regional surveys in progressively smaller population units, such as counties, then residential blocks, then homes.,13-14,Key Terms & Definitions,Sampling and Nonsampling Error,Population Parameter A value that accurately portrays or typifies a factor of a complete population, such as average age or income.,13-15,Key Terms & Definitions,Error that occurs because the sample selected is not perfectly representative of the population. All error other than sampling error - also called “measurement error.”,Sampling Error,Nonsampling Error,Sampling and Nonsampling Error,13-16,Key Terms & Definitions,A sample based on using people who are easily accessible such as mall intercepts or other high traffic locations. A sample in which the selection criteria are based on the researchers personal judgment about the representativeness of the population under study. The researcher selects who should be in the study.,Judgment,Convenience,Nonprobability Sampling,13-17,Key Terms & Definitions,A sample in which quotas, based on demographic or classif