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.
In establishing a national quota sample, you would need to know
what proportion of the national population is urban, eastern, male, under 25, white, working class and the like, and all the other permutations of such a matrix.
Once a matrix has been created and a relative proportion assigned to each cell in the matrix (quota sampling)
you collect data from persons having ALL the characteristics of a given cell
Quota sampling has several inherent problems.
- the quota frame (the proportions that different cells represent) must be accurate, and it is often difficult to get up-to-date information for this purpose.
- , biases may exist in the selection of sample elements within a given cell—even though its proportion of the population is accurately estimated.
Convenience Sampling
is almost never an adequate sampling method, although it is used all too frequently.
Convenience sampling is justified only if
the researcher wants to study the characteristics of people passing the sampling point at specified times.
The ____ and ____ of such a method explains its popularity, but it seldom produces data of any general value.
ease, cost
Convenience sampling is good for
pilot studies
In general, non-probability sampling methods are regarded as ____ ________ than probability sampling methods.
less reliable
Snowball sampling is
a type of purposive sampling that involves finding and recruiting participants through gatekeepers or referrals from existing participants.
Both purposive and snowball sampling are useful techniques for
qualitative research, as they allow you to select participants who can provide rich and relevant data.
Both purposive and snowball sampling have limitations
both techniques may introduce bias or limit generalizability as they do not ensure representativeness or randomness of the sample.
Sampling considerations involved in structured observations include
a discussion of the use of tables of random numbers that can be used to establish random samples of time, place, and activity.
Generalization of a sample only applies to
the population from which the sample was taken.
Non-response is reduced through:
callbacks, optimistic mannerism, not selling anything, appropriate attire, accommodating, personalization, ease of use, monetary incentive
