Chapter Ten Copyright © 2006 McGraw-Hill/Irwin Sampling: Methods and Planning

McGraw-Hill/Irwin 2 1.Distinguish between probability and nonprobability sampling methods. 2.Understand the advantages and disadvantages of probability sampling designs. 3.Understand the advantages and disadvantages of nonprobability sampling designs. 4.Illustrate the factors necessary for determining the appropriate sample design. 5.Understand the steps in developing a sampling plan. Learning Objectives

McGraw-Hill/Irwin 3 Exhibit 10.1 Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 4 Exhibit 10.2 Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 5 Types of Probability Sampling Designs Distinguish between probability and nonprobability sampling methods Simple Random Sampling Probability of Selection = Size of sample/Size of Population Advantages Disadvantages

McGraw-Hill/Irwin 6 Types of Probability Sampling Designs Distinguish between probability and nonprobability sampling methods Systematic Random Sampling (SYMRS) –Skip interval = defined target population list size/ desired sample size

McGraw-Hill/Irwin 7 Exhibit 10.4 Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 8 Types of Probability Sampling Designs Understand the advantages and disadvantages of nonprobagbility sampling designs Advantages –Easy to draw a sample –Economical Disadvantages –Hidden patterns –Must know exactly how many sampling units make up the defined target population

McGraw-Hill/Irwin 9 Types of Probability Sampling Designs Distinguish between probability and nonprobability sampling methods Stratified Random Sampling (STRS) –Goal –Three basic steps for drawing a STRS –Two common methods used Proportionate stratified method Disproportionate stratified method –Optimal allocation

McGraw-Hill/Irwin 10 Exhibit 10.5 Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 11 Types of Probability Sampling Designs Understand the advantages and disadvantages of probability sampling designs Advantages –Assurance of Representativeness –Opportunity to study each stratum –Ability to make estimates Disadvantages –Difficult in determining the basis for stratifying

McGraw-Hill/Irwin 12 Types of Probability Sampling Designs Distinguish between probability and nonprobability sampling methods Cluster Sampling –Each cluster is representative of the heterogeneity of the target population –Area sampling One-step approach Two-step approach

McGraw-Hill/Irwin 13 Exhibit 10.6 Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 14 Types of Probability Sampling Designs Advantages –Cost effectiveness –Ease of implementation –Often only reliable method available Disadvantages –Tendency for clusters to be homogeneous in nature –Appropriateness of the factors used to sample within clusters Understand the advantages and disadvantages of probability sampling designs

McGraw-Hill/Irwin 15 Types of Nonprobability Sampling Designs Distinguish between probability and nonprobability sampling methods Convenience Samples –Drawn based at the convenience of the researcher Assumption

McGraw-Hill/Irwin 16 Types of Nonprobability Sampling Designs Advantages –Large number of respondents –Used in early stage of research Disadvantages –Problems of reliability –Do respondents represent the target population –Results are not generalizable Understand the advantages and disadvantages of nonprobability sampling designs

McGraw-Hill/Irwin 17 Types of Nonprobability Sampling Designs Judgment sampling –Selected based on an experienced individual’s belief Advantages –Based on the experienced person’s judgment Disadvantages –Cannot measure the respresentativeness of the sample Distinguish between probability and nonprobability sampling methods

McGraw-Hill/Irwin 18 Types of Nonprobability Sampling Designs Distinguish between probability and nonprobability sampling methods Quota sampling –Based on prespecified quotas regarding demographics, attitudes, behaviors, etc Advantages –Contains specific subgroups in the proportions desired –May reduce bias Disadvantages –Dependent on subjective decisions –Not possible to generalize

McGraw-Hill/Irwin 19 Types of Nonprobability Sampling Designs Distinguish between probability and nonprobability sampling methods Snowball Sampling –Respondents identify additional people to included in the study The defined target market is small and unique Compiling a list of sampling units is very difficult

McGraw-Hill/Irwin 20 Types of Nonprobability Sampling Designs Advantages –Identifying small, hard-to reach uniquely defined target population –Useful in qualitative research Disadvantages –Bias can be present –Limited generalizability Understand the advantages and disadvantages of nonprobability sampling designs

McGraw-Hill/Irwin 21 Exhibit 10.7 Critical Factors in Selecting the Appropriate Sampling Design Illustrate the factors necessary for determining the appropriate sample design

McGraw-Hill/Irwin 22 Exhibit 10.8 Steps Involved in Developing a Sampling Plan Understand the steps in developing a sampling plan

McGraw-Hill/Irwin 23 Summary Value of Sampling Methods in Marketing Research Types of Probability Sampling Designs Types of Nonprobability Sampling Designs Determining the Appropriate Sampling Design Steps in Developing a Sampling Plan

McGraw-Hill/Irwin 24 The End Copyright © 2006 McGraw-Hill/Irwin