Slide 7.1 Chapter Selecting Samples Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.2 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.3 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.4 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.5 Selecting samples Population, sample and individual cases Source: Saunders et al (2009) Figure 7.1 Population, sample and individual cases Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.6 The need to sample Sampling- a valid alternative to a census when • A survey of the entire population is impracticable • Budget constraints restrict data collection • Time constraints restrict data collection • Results from data collection are needed quickly Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.7 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.8 Overview of sampling techniques Sampling techniques Figure 7.2 Sampling techniques Source: Saunders et al (2009) Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.9 The sampling frame • The sampling frame for any probability sample is a complete list of all the cases in the population from which your sample will be drown Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.10 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.74 Critical case sampling • Critical case sampling selects critical cases on the bases that they can make a point dramatically or because they are important The focus of data collections to understand what is happening in each critical case so that logical generalizations can be made Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.75 Continued • Patton (2002) outlines a number of clues that suggest critical cases these can be summarized by the questions such as: • If it happens there, will it happen everywhere? • If they are having problems, can you be sure that everyone will have problems? • If they cannot understand the process, is it likely that no one will be able to understand the process? • Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.76 Typical case sampling • In contrast of critical case sampling, typical case sampling is usually used as a part of a research project to provide an illustrative profile using a representative case Such a sample enables you to provide an illustration of what is ‘typical’ to those who will be reading your research report and may be unfamiliar with the subject matter It is not intended to be defintative Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.77 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.78 Snowball sampling • Is commonly used when it is difficult to identify members of desired population For example people who are working while claiming unemployment benefit you therefore, need to: Make contact with one or two cases in the population Ask these cases to identify further cases Ask theses new cases to identify further new cases (and so on) Stop when either no new cases are given or the sample is as large as manageable Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.79 Self selecting sampling • It occurs when you allow each case usually individuals, to identify their desire to take part in the research you therefore Publicize your need for cases, either by advertising through appropriate media or by asking them to take part Collect data from those who respond • Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.80 Self-selection sampling • Publicity for convenience samples can take many forms These include articles and advertisement in magazines that the population are likely to read, postings on appropriate Internet newsgroups and discussion groups, hyperlinks from other websites as well as letters or emails of invitation to colleagues and friends (Box 7.14) Cases that self-select objectives In some instances ,as in research question(s) or stated on the management of the survivors of downsizing (Thornhill et al.1997), this is exactly what the researcher wants In this research a letter in the personnel trade press generated a list of self-selected organisations that were interested in the research topic , considered it important and were willing to devote time to being interviewed Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.81 Convenience sampling • Convenience sampling (or haphazard sampling) involves selecting haphazardly those cases that are easiest to obtain for your sample, such as the person interviewed at random in a shopping centre for a television programme or the book about entrepreneurship you find at the airport (Box 7.15) The sample selection process is continued until your required sample size has been reached Although this technique of sampling is used widely , it is prone to bias and influences that are beyond your control, as the cases appear in the sample only because of the ease of obtaining them Often the sample is intended to represent the total population , for example managers taking an MBA course as a surrogate for all managers! In such instances the selection of individual cases is likely to have introduced bias to the sample ,meaning that subsequent generalisations are likely to be at best flawed These problems are less important where there is little variation in the population, and such samples often serve as pilots to studies using more instructed samples Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.82 Probability sampling • With probability samples the chance , or probability, of each case being selected from the population is known And usually equal to all cases This means that it is possible to answer research questions and to achieve objectives that require you to estimate statistically the characteristics of the population from the sample Consequently, probability sampling is often associated with survey and experimental research strategies Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.83 Non probability samples • The probability of each case being selected from the total population is not known and it is impossible to answer research questions or to address research objectives that require you to make statistical inferences about the characteristics of the population You may still be able to generalize from non probability samples about the population, but non on statistical grounds Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.84 Non- probability sampling (1) Key considerations • Deciding on a suitable sample size • Selecting the appropriate technique Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.85 Non- probability sampling (2) Sampling techniques • • • • • Quota sampling (larger populations) Purposive sampling Snowball sampling Self-selection sampling Convenience sampling Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.86 Summary: Chapter • Choice of sampling techniques depends upon the research question(s) and their objectives • Factors affecting sample size include: - confidence needed in the findings - accuracy required - likely categories for analysis Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.87 Summary: Chapter • Probability sampling requires a sampling frame and can be more time consuming • When a sampling frame is not possible, nonprobability sampling is used • Many research projects use a combination of sampling techniques Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.88 Summary: Chapter All choices depend on the ability to gain access to organisations Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 ... Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.3 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th. .. Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.7 Saunders, Lewis and Thornhill, Research Methods for Business Students, 5th. .. Thornhill, Research Methods for Business Students, 5th Edition, © Mark Saunders, Philip Lewis and Adrian Thornhill 2009 Slide 7.10 Saunders, Lewis and Thornhill, Research Methods for Business Students,