ch 4 Flashcards
two types of statistics
descriptive
inferetial
three types of non-probability sampling
convenience sampling
snowball sampling
quota sampling
multi-stage cluster sampling involves _______stages
two or more
- selecting clusters (groups of elements)
- selecting subunits within cluster
- randomly sampling within the clusters
what are multi-stage cluster sampling used for
large populations (no adequate sampling frame, elements are geographically dispersed)
how to select a stratified random sample
stratify the population (divide into subgroups)
select a simple random sample or a systematic sample from each stratum
in stratified random sampling ensure that _____ in the population of ______ represented in the sample
subgroups
proportionally
explain systematic sample
selected from sampling framing (no random. numbers)
- choose a number at random from 1 to i (size of sampling interval)
- this number is known as a random start
about what percent of all sample means lie within 1.96 standard errors off the mean
95%
what is a sampling frame
a list of elements in the population
how many people you ask to get a good estimate depends on
the level of variability
when there is low variability you do not have to ask as many people to get an ______ response
accurate
four types of probability samples
simple random sample
systematic sample
stratified random sampling
multi-stage cluster sampling
what does standard error of the mean measure
probability samples with sufficient sample sizes that have minimal sampling error
probability samples with sufficient sample sizes minimize the amount of
sampling error (but it is still bound to occur)
is it virtually impossible to eliminate sampling error, why?
yes, using random samples and making the samples as large as possible helps to minimize sampling error
when do errors of estimation occur
when there is a discrepancy between the sample and the total population
Sampling
the selection of a subset of a population
for observation
what are the two main sampling types
- Probability: Uses random selection methods, associated
with quantitative methods. - Non-probability: Does not use random selection methods,
associated with qualitative research.
systematic
A probability sampling method in which units are selected from a sampling frame at fixed intervals (for example, every fifth un
cluster sample
A procedure in which the researcher first samples sets of cases (“clusters”) and then samples units within them, usually using a probability sampling method.
non-probability sampling
A sample selected using a non-random sampling method. Essentially, this means that some units in the population are more likely than others to be selected.
quota sampling
A type of non-probability sample that matches the proportions of people in different categories in the population
sampling error
Differences between the characteristics of a random sample and the population from which it is selected.
Element or unit:
A single case in the population. In the social sciences that element or unit is usually a person, but many other things can be sampled as well: nations, cities, regions, schools, firms, and so on. Finch and Hayes (1994), for example, based part of their research on a random sample of wills of deceased people
population
All the cases about which you are seeking knowledge, or all the cases to which your conclusions are meant to apply
sampling frame
The list of elements from which the sample will be selected
probability sample
A sample selected using a random process such that each unit in the population has a known chance of being selected. The aim of probability sampling is to keep sampling error (see below) to a minimum
Non-response
A situation that occurs whenever some unit selected for the sample refuses to participate in the study, cannot be contacted, or for some other reason does not supply the required data.
Census:
Data collected from all elements in the population rather than from a sample. The phrase “the census” typically refers to the enumeration of all (or nearly all) members of the population of a nation-state—that is, a national census
Sampling error
An error of estimation that occurs if there is a difference between the characteristics of a sample and those of the population from which it was selected. Sampling error can occur even when a random method is used
what is the sampling ratio
n/N
systematic sample is directly from the
sampling frame without using random numbers
In systematic sampling, it is important to ensure that there is no
pattern or ordering, a feature called periodicity.