The entire set of subjects that are of interest to the researcher
A carefully selected subset of the population that refelcts the composition of that population
A statistical value that indicates differences in results found in the sample compared to the population from which the sample was drawn
In quantitative study the sampling strategy is aimed at maximizing the potential for generalization or the ability to apply the findings to larger groups
A condition that occurs when subjects are selected for a study or assigned in groups in a way that is not impartial. This may pose a threat to the validity of the study. Controlled almost exclusively by a sound sampling strategy.
Having an adequate number of subjects provides the study with power
The ability to detect effects
The first step of a sampling strategy is:
To clearly define the population of interest
The potential participants who meet the definition of the populatino and are accessible to the researcher
The selection strategy involves making decisions about how subjects will be recruited, selected, and if appropirate, assigned to groups.
The goal of the selection strategy is to:
Support validity of the study
Enhance credibility of the results
A homogenous sample is one in which the subjects are very similar in characteristics, and it makes generalizing to other populations difficult
In qualitative research, the goal of selection strategy is credibility rather than generalizability so selection methods are purposive
Guidelines for choosing subjects with a predetermined set of characteristics that include major factors important to the research question
Characteristics that eliminate a potential subject from the study.
A technique used in qualitative reserarch in which the subjects are selected because they possess certain characteristics that enhance the credibility of the study
Quantitative samples are best when they are selected and assigned to groups randomly
A sampling process used in quantitative research in which every member of the available population has an equal probability of being selected for the sample
Probability or random sampling
The only way to be sure a sample represents a population is if it incorporates two essential criteria:
Each member of the pop has an equal probability of selection for the sample
Each subject selection is an independent event
A condition that occurs when the selection of one subject has no influence on selection of other subjects; each member of the population has exactly the same chance of being in the sample
Samples are structured so that important characteristics are evenly distributed across all groups
Stratified random sampling
Sample in which the first subject is drawn randomly and the remaining subjects are selected at predetermined intervals
Systematic random sampling
Researcher randomly selects entire groups and then randomly selects subjects from only those groups
Cluster random sampling
A nonprobability method of selecting a sample that includes subjects who are available conveniently to the researcher
Sampling is used when a table of random numbers is used to select subjects rom the sampling frame.
Simple random sampling
A nonprobability sampling method that relies on referrals from the initial subjects to recruit additional subjects
Snowball or referral sampling
The definition of the major entity or subject that will be analyzed in the study
Unit of analysis
The standard for a sample size in a qualitative study is:
The achievement of saturation
Saturation has been achieved when the researcher concludes that responses are repetitive, and no new info is being generated.
An analysis that indicates how large a sample is needed to adequately detect a difference in the outcome variable
Big effects are easier to see in the data, just as a large object is easier to see than a small one
This error occurs when there is a difference between groups but the researcher does not detect it. (The intervention works but researchers do not detect it)
Type II error
The ability to generalize the findings from a research study to other populations, places, and situations.
The link between finding knowledge through research and using knowledge in practice
A type of external validity where the findings can be generalized and applied to other settings
A type of external validity where the findings can be generalized and applied to other subjects
Subjects who have a personal interest in the study are more likely to complete it. A combination of personal enthusiasm and nurturing by the researcher is often necessary to keep subjects in a study.
Samples with at least 80% power are desirable
If statistical significance was achieved, the sample had sufficient power