QN Research Sampling Terms

Sampling

Selecting a group of people, events, behaviors, or other elements with which to conduct a study

Element (a.k.a. case)

An individual unit of a population can be a person (subject), event behaviour

Sample

Selected group of elements from which data are collected for study

Target population

Group to whom the researcher aims to generalize/transfer findings

Accessible population

The portion of the target population to which the researcher has reasonable access, (reduces cost and more feasible)

Generalizability

The degree to which data are representative of similar phenomena in a population beyond the study sample

Representativeness

Key characteristics of the sample are similar to those of the population (sample accessible population, and the target are alike in as many ways as possible)

Homogeneity

Degree to which subjects are similar (decrease generalizability)

Heterogeneity

Degree to which subjects are different (increase generalizability)

Sampling error

Difference between the values of a sample statistic and a population statistic (explains why values will differ from one sample to another drawn from the same population)

Sampling frame

A listing of every member of the population using the sampling criteria to define membership in the population (subjects are selected from this)

Sampling plan

Outline strategies used to obtain a sample for study (who, where, when, how?)

Probability (random) sampling

Every individual in the population should have an opportunity to be selected for a sample

Simple random

Element selected randomly from sampling frame

Stratified random

Used when certain variables are considered critical to representativeness

Cluster (multistage)

Elements drawn from chosen “mini representations” of the target population

Systematic

Selecting every “nth” element from a complete list of the population using a random starting point

Non-probability (non-random) sampling

Not every element in the population has an opportunity to be included in the sample

Convenience

Elements are enrolled based on availability. Researcher enrolled until desired sample size is achieved.

Quota

Similar to stratified sampling but initial sample is not random

Network (snowball)

Initial subjects are enrolled by convenience than additional subjects are identified through association

Purposive

Research or select subjects based on judgement about who will provide the most useful data to answer the research question

Theoretical

Used in grounded theory research

Power

Capacity of the study to detect actual differences or relationships. Capacity of the study to correctly reject the null hypothesis. Indicates the number of participants required to avoid a type two error in a comparative study. ( .80 minimal acceptable level.)

Affect size

A statistical expression of the magnitude of the relationship between two variables or the difference between two groups (.2 small, .5 medium, .8 large)