Cheatography
https://cheatography.com
Be able to
- Describe what ‘nonprobability sampling’ is and identify several techniques.
- Identify, describe and explain several types of probability sampling.
- Evaluate choices of ‘nonprobability sampling’ and ‘probability sampling’ in relationship
to the research questions.
- Explain the relationship between (research) populations and sampling frames in social
research.
- Describe the steps involved in selecting a multistage cluster sample
This is a draft cheat sheet. It is a work in progress and is not finished yet.
qualititative method
- interviews or participation observation
- Purpose: explorative and explanatory
- Labour intensive: low numbers objects of study
- Often nonprobability sampling
- In-depth insights |
quantitative method
- Questionnaires or/and surveys
- Purpose: descriptive and explanatory
- With little effort high numbers objects of study
- Probability sampling
- Generalizable |
choice of subjects
*Rather than studying the complete (research) population, social scientists mostly select (relatively few) people for study to discover things that apply to many more people who are not
studied, at least so can be claimed to a certain extent.*
in probability sampling there are 4 ways in which objects of study can be selected:
1. Simple random: assign numbers to sampling frame and select numbers randomly (computer) -> each element has an equal chance of being selected
2. Systematic: every kth unit in a list is selected in the sample
3. Stratified: grouping of the units composing a population into homogeneous groups before sampling.
4. Cluster: natural groups (clusters) are sampled initially, with the members of each selected group being subsampled afterwards |
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nonprobability sampling
nonprobability = chance to became part of a sample is unknown
- in general use:
→ Qualitative research
→ Populations with no sampling frame
- Nonprobability sampling, how are objects of study selected?
4 types:
1. Convenience: easy availability of objects of study
2. Snowball: ask objects of study to suggest additional objects
3. Purposive: researcher’s judgment about which objects of study will be the most useful or representative
4. Quota: on the basis of pre-specified characteristics, so that the sample will have the same distribution of characteristics assumed in the population |
problem of nonprobability samples: bias
→ i.e. personal/practical (i.e. easy availability) preferences researcher
sample errors, confidence level and interval
statistic: the summary description of a variable in a sample, used to estimate a population parameter
Sampling error: the degree of error to be expected of a given sample instead of the population
→ decrease when sample numbers increase + when variations decrease
Confidence level: the estimated probability that a population parameter lies within a given confidence interval
Confidence interval: the range of values within which a population parameter is estimated to lie |
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probability samples
purpose of empirical research = representativeness
→ and so, sample of objects of study from a population must contain the same variations that exist in the population
+ the quality of a sample of having the same distribution of characteristics as the population from which it was selected
method:
- sample of objects of study from a population must contain the same variations that existin the population
- the quality of a sample of having the same distribution of characteristics as the population from which it was selected |
advantages probabiity sampling:
- are typically more representative than nonprobability samples as biases are avoided
- probability theory permits researchers toe estimate the accuracy or representativeness of the sample
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