Sampling Flashcards
target population (reference population):
refers to the group of individuals to which results of the study are applied to; who we are going to study
population:
the general group of people from whom information is needed
accessible population
the actual population of subjects available to be chosen for a study. This group is usually a nonrandom subset of the target population.
the cases included in the study are the “____”
sample
sampling bias
bias that occurs when individuals who are selected for a sample over-represent or underrepresent the underlying population characteristics
sample:
a collection of subjects (a noun)
simple random sample:
A probabilistic sampling method in which each potential subject has an equal chance of being selected
inclusion criteria:
A list of specific attributes that will make an individual (or a unit of analysis such as an organization) eligible for participation in a specific study.
exclusion criteria:
A list of characteristics that may influence, or “confound,” the outcomes of a study; researchers use these criteria to eliminate individuals (or units of analysis such as an organization) with these characteristics as subjects in a study
sampling frame:
A list of potential subjects obtained from various public or private sources
extraneous variables:
Individual, organizational, or environmental characteristics other than the factor of interest (i.e., test, predictor, intervention) that may influence the outcome of a study
sampling:
the method for selecting individuals for a study, also called “selection”
probabilistic sampling:
Methods for choosing subjects that use a random selection process to increase the chance of obtaining a sample that accurately represents the population from which it is drawn
nonprobabilistic sampling:
Methods for choosing subjects that do not use a random selection process; as a result, the sample may not represent accurately the population from which it is drawn.
cluster sampling:
A form of probability sampling in which large subgroups (clusters) are randomly selected first, and then smaller units from these clusters are successively chosen; also called multistage sampling.
convenience sampling:
A nonprobability sampling procedure, involving selection of the most available subjects for a study
purposive sampling:
A nonprobability sample in which subjects are specifically selected by the researcher on the basis of subjective judgment that they will be the most representative
snowball sampling:
A nonprobability sampling method in which subjects are successively recruited by referrals from other subjects.
stratified random sampling:
A probabilistic sampling method in which subgroups of a population are identified and randomly selected to ensure their inclusion in a study
systematic sampling:
A probabilistic sampling method in which the first subject is randomly selected from a group organized according to a know identifier (such as birth date) and then all remaining subjects are chosen based on their numerical distance from the first individual.
assignment:
putting subjects into groups, also called “allocation”
block assignment
An assignment method in which the number of individuals in each group is predetermined; investigators randomly assign subjects to one group at a time until each quota is met.
masked (blinded):
(1) In diagnostic test and clinical measure papers, the lack of knowledge about previous test/measure results; (2) in prognostic factor papers, the lack of knowledge about exposure status; and (3) in intervention papers, the lack of knowledge about to which group a subject has been assigned
matched assignment:
An assignment method in which subjects are first divided into subgroups based on a specific characteristic such as age, gender, and so forth; members of each subgroup are then randomly assigned to each group in the study to balance the characteristics across the groups.