Ch.5 Flashcards
Sample
The process of drawing a number of individual cases from larger population
Why do we need to sample ?
Because studying every single instance is impractical or too expensive.
When would it be unnecessary to sample?
When the number of things we want to examine is small , when data are easily accessible and when data quality is unaffected but the number of things we look at.
Element
A kind of thing a researcher wants to sample
Population
The group of elements from which a researcher samples and to which she or he might like to generalize
Sample
A number of individual cases drawn from a larger population
Sampling frame or study population
The group of elements from which a sample is actually selected
Non probability samples
Samples that have been drawn in a way that doesn’t give every member of the population a known chance of being selected
Probability samples
Samples drawn in a way to give every member of the population a known (nonzero) chance of inclusion
Biased samples
Samples that are unrepresentative of the population from which they been drawn
Generalizability
The ability to apply the results of a study to groups or situations beyond those actually studied
Coverage error
An error that results from different between the sampling frame and the target popular
No response error
An error that results from differences between non responses and responders in a survey
Sampling error
Any difference between sample characteristics and the equivalent characteristics in the sampling frame when this difference is not due to non response error.
Parameter
A summary of variable characteristics in a population
Statistic
A summary of a variable in a sample
Random digit dialing
A method for selecting participants in a telephone survey that involves randomly generating telephone numbers
Sampling variability
The variability in sample statistics that can occur when different samples are drawn from the same population
Simple random sample
A probability sample in which every members of the study population has been given an equal chance of selection
Margin of error
A suggestion of one far away the actual population parameter is likely to be from the statistic
Systematic sampling
A probability sampling procedure that involves selecting every kth element from a list of population elements after the first element has been randomly selected
Systematic sampling advantages
The relative ease do selecting a systematic sample as one of the procedures advantages and of gut population is present (file,folders) you don’t need to make a list.
Systematic sample disadvantages
It can introduce an error if the sampling frame is cyclical in nature.
Stratified sampling
A probability sampling procedure that involves dividing the population in groups or strata defined by the presence of certain characteristics and then random sampling from each stratum.
Stratified sampling diadvantages
It can yield samples that are flawed in ways you want to avoid and can can do something about it.
Cluster sampling
A probability sampling procedure that involves randomly selecting clusters of elements from a population and subsequently selecting every element in each selected cluster for inclusion in the sample
Multistage sampling
A probability sampling procedure that Involves several stages such as randomly selecting clusters from a population then randomly selecting elements from each of the clusters
Purposive sampling
A non probability sampling procedure that involves selecting elements based on the researchers judgement about which elements will facilitate his or her investigation
Quota sampling
A non probability sampling procedure that involves describing the target population in term of what are thought to be the relevant criteria and then selecting sample elements to represent the relevant sub groups in proportion to their presence in the target population
Snow ball sampling
A non probability sampling procedure that involves suing members of the group of interest to identity other members of the group
Convenience sampling
A group of elements that are readily accessible to the researcher
