186857
Description
Mind Map by shirley.ha, updated more than 1 year ago
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Created by shirley.ha
about 11 years ago
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Non-probability
sampling
methods
- used for practical reasons
- sually easier and cheaper to implement, but they may result in
samples that are less representative of the whole population.
- sually easier and cheaper to implement, but they may result in
samples that are less representative of the whole population.
- Convenience
- involves selecting a sample from a convenient location without
considering the degree to which the sample is representative.
- Clinical health research uses this
- taking the patients/participants who are available - as random
sampling from the population is almost impossible
- involves selecting a sample from a convenient location without
considering the degree to which the sample is representative.
- Quota
- Under conveience
- and setting quotas for sub-groups prior to convenience sampling.
- and setting quotas for sub-groups prior to convenience sampling.
- Individuals who have certain characteristics of interest
are selected from a convenient location until the required
sample size is reached (the quota).
- Under conveience
- Snowball
- using networks to identify a sample.
- Used when sample frames not available
- Used when sample frames not available
- uses the first few participants with the desired
characteristics to identify similar people to
enlarge the group.
- Ppl who meet criteria are selected
- Collect the info
- asked to identify other individuals who meet
the sampling criteria
- asked to identify other individuals who meet
the sampling criteria
- Collect the info
- Ppl who meet criteria are selected
- using networks to identify a sample.
- Purposive
- researcher making a decision about who will be able to
provide the desired information and only sampling from
these identified individuals.
- participants are handpicked as they have the information needed.
- used when the population of interest is very small
and it would not be practical or economical to
sample the general population in order to identify
them.
- researcher making a decision about who will be able to
provide the desired information and only sampling from
these identified individuals.
- Is the sample rep of the whole pop?
- Consider if adequate in size, is accurate in its
characteristics and is complete.
- consider the sampling method to be used.
- Statisticians
- use sampling distribution theory to help them
to estimate how representative a sample is in
relation to the target population
- Sampling error
- discrepancy between our sample mean and the true
population mean (average).
- calculated from the sample size and the amount of variability in the sample.
- sample mean is rarely exactly equal to the population mean
- expect the sample mean to be close to the
population mean (i.e. to estimate the population
mean) provided we have used a robust sampling
method.
- expect the sample mean to be close to the
population mean (i.e. to estimate the population
mean) provided we have used a robust sampling
method.
- sample mean is rarely exactly equal to the population mean
- discrepancy between our sample mean and the true
population mean (average).
- use sampling distribution theory to help them
to estimate how representative a sample is in
relation to the target population
- Statisticians
- consider the sampling method to be used.
- Consider if adequate in size, is accurate in its
characteristics and is complete.
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