QUALITATIVE METHODS SAMPLING

I. POPULATION & SAMPLE A. Qualitative social science aims to describe a population acting within a particular scene or setting.  1. A population is group or class of subjects, variables, concepts, etc. (texts are called a universe).  2. If whole population is studied, called a census.  3. Relevant characteristics of population are called parameters.  4. Select with some type of sampling frame. B. For qualitative work, obtain samples from the population, because almost impossible to observe every aspect of a scene, event, etc.

II. Types of sampling A. Two basic types of samples:  1. Random (Probability) a. Selected by mathematical guidelines. b. Each person has an equal chance of being selected.  2. Non-random (Non-probability)--does not follow the guidelines of mathematical probability.  3. Random samples are unnecessary in qualitative work since not looking to generalize. a. However, are looking for frequencies b. Often can get enough data via certain kinds of sampling strategies

II. Types of sampling B. In determining the type of sample to use, need to determine a sampling unit. C. Other considerations:  1. Does the sampling strategy provide the greatest value for the least investment?  2. What are the time and budget constraints?  3. Does the sampling strategy permit enough relevant data to be collected?

II. Types of sampling D. Criterion Sampling  1. Select persons, activities, events, sites, settings, texts based on some stated criterion  2. Usually stated in inclusionary terms, but can also exclude people  3. Criteria can be derived from theory or from commonly understood definitions of the case.  4. Can let subjects determine the criteria as well.

II. Types of sampling  5. One type of criterion sampling is the Purposive (aka Purposeful or Strategic Sample) a. Respondents are non-randomly selected on the basic of a particular characteristic (e.g. race, gender, age, viewing habits, etc.) b. Often used in advertising studies, as well as in naturalistic research. E. Quota Sample  1. Respondents selected non-randomly on the basis of their known proportion in a population.  2. Also used more often in market research

II. Types of sampling F. Maximum Variation Sampling  1. Taps into a range of qualities, attributes, situations, or incidents of phenomenon  2. Seeks to include as much diversity from the population as possible  3. If combined with other techniques (triangulation), can get a fairly good representation of the population

II. Types of sampling G. Network Sample (aka Multiplicity Sample, Snowball Sample)  1. Respondents refer or recruit other respondents for the study  2. Those respondents then do the same  3. These chains of referrals create a growing pool of respondents (like ripples on a pond or a snowball going down a hill)  4. Good for studying social networks  5. Snowballs can “freeze” or “melt” prematurely  6. Alternatively, can grow too fast, creating too much data

II. Types of sampling H. Typical-Case Sampling  1. Attempts to capture the normative form of a phenomenon—the typical case  2. Typicality is not representation a. Not designed to make generalized statements b. “The sample is illustrative, not definitive” (Patton, 1990, p. 173). I. Atyptical-case Sampling  1. Looks to the rare, exotic, controversial, etc. (the “outliers”)  2. Understanding the case is the point of the study

II. Types of sampling J. Convenience Sample (aka Available Sample)  1. Sampling anyone who will cooperate—a collection of readily accessible subjects.  2 Subjects selected non-randomly because they are available  3. Not usually the best for qualitative work since often doesn’t meet the conditions of the study  4. A variant is the volunteer sample (see below)

II. Types of sampling K. Volunteer sample  1. Subjects volunteer to be part of the study; often due to some type of monetary or tangible reward  2. Used more in market or proprietary research (especially focus groups)  3. Again, the sample chosen might not reflect the goals of the study or population parameters  4. Often useful in pre-testing questionnaires or other preliminary research  5. Both volunteer and convenience samples have potential external validity problems

III. Sample Size A. How large must a sample be to provide the desired results?  1. No one set answer for either quantitative or qualitative research  2. Several factors influence: a. The type & purpose of project b. The project’s complexity (its scope, the scene, etc.) c. The time constraints of the project d. The financial constraints on the project e. Previous research in the area

III. Sample Size B. For qualitative work, no hard or fast rules  1. Usually an iterative process—start with a few instances or subjects and add in new ones to support emerging theorizing (stopping when responses begin to repeat)  2. For a tight-knit group, can study the whole population  3. Practical issues can intervene (e.g. mortality effects—people dropping out, etc. & other unforeseen events)  4. Consider sample size norms for type of research conducting (information often available in published research)

III. Sample Size 5. Consider research methodology  a. Participant observation depends on the setting  b. Interviewing may only need a few samples  c. Focus groups or naturalistic studies usually use small samples (6-12 participants), because of the need to moderate the discussion 1) Should recruit a larger sample than required 2) Affected by mortality effects & no shows  d. Qualitative content or discourse analysis may have large samples (e.g. 1000s of lines of discourse)  e. Critical work or other case studies may have a very small sample (can even have a sample of N=12