chapter 7 Flashcards
to generalize to the population composing the sampling frame
it is necessary for all elements to have equal representation in the frame
Sampling frame
the list or quasi-list of elements from which a probability sample is selected.
how many times should each element appear in a sampling frame?
once
2 reasons why simple random sampling is seldom used
- with all but the simplest sampling frame, simple random sampling is not feasible.
- simple random sampling may not be the most accurate method of sampling available.
sampling interval
which is the standard distance between elements selected in the sample. population size/sample size
To ensure against any possibility of human bias in systematic sampling
you should select the first element at random and then proceed to select every 10th element afterwards.
2 terms are frequently used in connection with systematic sampling.
- Sampling interval
- Sampling ratio
sampling ratio
the proportion of elements in the population that are selected in the example. sample size/population size
In practice, systematic sampling is virtually identical to
simple random sampling
Stratified sampling
is a method for obtaining a greater degree of representativeness—decreasing the probable sampling error.
sampling error is reduced by 2 factors.
- a large sample produces a smaller sampling error than a small sample.
- a homogeneous population produces samples with smaller sampling error than does a heterogeneous population.
For stratified samples, researchers divide
a heterogeneous population into homogeneous subsets, or subpopulations, called ‘strata
Methods of stratification in sampling vary. When you are working with a simple list of all elements in the population two are predominant.
- to sort the population elements into discrete groups based on whatever stratification variables are being used.
- group elements as described and then put those groups together in a continuous list
Stratified sampling ensures
the proper representation of the stratification variables
a stratified sample is likely to be more representative on a number of variables than
A simple random sample
Cluster sampling may be used when
it is either impossible or impractical to compile an exhaustive list of the elements composing the target population.
Multistage cluster sampling, then, involves the repetition of 2 basic steps:
Listing and sampling
Whatever the situation, however, ___________ _____________ remains the most effective method for selection of study elements.
Probability sampling
Why is probability sampling the most effective method for selection of study elements?
- it avoids conscious or unconscious biases in element selection on the part of the researcher.
- it permits estimates of sampling error.
non-probability sampling is used when
- it is not possible to use standard probability sampling methods.
- it is not even appropriate to use probability sampling methods
Use purposive sampling when
it is appropriate for you to select your sample on the basis of your own knowledge of the population, its elements, and the nature of your research aims
Purposive sampling is best serves what chronological purpose in research?
test/pilot studies (a pretest)
Quota sampling begins with
a matrix describing the characteristics of the target population.
quota sampling addresses the issue of
representativeness, though the two methods approach.
