Chapter 6 - Criminal Justice and Criminology Research Methods, 2nd Edition

Sampling in Crime and Justice Research Chapter 6 1 Vocabulary of Sampling Sampling: A smaller set of cases that a researcher selects from a larger pool and generalizes to the population. Sampling Case: The name for a single unit to be sampled is sampling case. Population: The abstract idea of a large group of many cases from which a researcher draws a sample and to which results from a sample are generalized. 2 Vocabulary of Sampling (cont.) Target Population: The concretely specified large group of many cases from which a researcher draws a sample and to which results from a sample are generalized. Sampling Frame: A specific list or set of boundaries within a population from which a researcher chooses her or his sample (e. g., telephone director, driver’s license records). Population Parameter: A characteristic of the entire population that is estimated from a sample. 3 Random Sampling Random Sample: A sample in which the researcher uses a random number table or similar mathematical random process so that each sampling element in the population will have an equal probability of being selected. Sampling Error: How much a sample deviates from being representative of the population. Simple Random Sample: A random sample in which a researcher creates a sampling frame and uses a pure random process to select cases so that each sampling element in the population will have an equal probability of being selected. 4 Central Limits Theorem Sampling Distribution: A distribution created by drawing many random samples from the same population. Central Limit Theorem: A mathematical relationship that states that random samples will form a normal distribution. Confidence Intervals: A range of values within which a researcher has a specified and high degree of confidence that the populations parameters lies. 5 Types of Random Sampling Systematic Sampling: A random sample which selects every kth (e. g., 12th) case in the sample frame using a sampling interval. Sampling Interval: The inverse of the sampling ration that is used when selecting cases in systematic sampling. Stratified Sampling: A random sample that identifies a set of mutually exclusive and exhaustive categories, divides this frame by categories, and uses random selection to select cases from each category. 6 Types of Random Sampling Cluster Sampling: A random sample using multiple stages to cover wide geographic areas in which aggregated units are randomly selected and then samples are drawn from the sampled aggregates. Random-digit Dialing (Rdd): A method of randomly selecting cases for telephone interviews that uses all possible telephone numbers as a sampling frame. 7 Non-Probability Sampling Nonrandom Sample: A sample using something other than a mathematically random process. Haphazard Quota Purposive Snowball Deviant Case Sequential Theoretical 8 Haphazard and Quota Sampling Haphazard Sampling: A nonrandom sample in which the researcher selects anyone he or she happens to come across. Quota Sampling: A nonrandom sample that identifies general categories into which cases will be selected to reach a predetermined number in each category. 9 Purposive Sampling Purposive Sampling: A nonrandom sample in which the researcher uses a wide range of methods to locate all possible cases of a highly specific and difficult-to-reach population. 10 Snowball and Deviant Case Sampling Snowball Sampling: A nonrandom sample that begins with one case and then identifies other cases, and repeats the process again and again. Deviant Case Sampling: A nonrandom sample that selects unusual or nonconforming cases purposely as a way to provide greater insight into social processes or a setting. 11 Sequential and Theoretical Sampling Sequential Sampling: A nonrandom sample that finds as many relevant cases as possible, until resources are exhausted, or until no new information arises. Theoretical Sampling: A nonrandom sample that selects specific times, locations, or events to observe to develop a social theory or evaluate theoretical ideas. 12 Hidden Populations Hidden Populations: A population of people who engage in clandestine, socially disapproved, or concealed activities and who are difficult to locate and study. Mixed Sampling Approach: An approach to sampling that involves mixing qualitative and quantitative styles of research and combining probability with nonprobability techniques. 13