Ch 7. Quantitative Sampling Flashcards
the selection of a subset of a population for research
Sampling
Two main types of sampling
- Probability: Uses random selection methods
- Non-probability: Does not use random selection methods
Three sources of bias in sampling
- not using a random method to pick the sample
- the sampling frame
- non-response
Errors of estimation that occur because there is a discrepancy between the sample group and the total population
Sampling Error
It is virtually impossible to eliminate what?
sampling error. So, using random samples and making the samples as large as possible helps minimize sampling error.
4 Types of Probability Sample
Simple random sample
Systematic sample
Stratified random sampling
Multi-stage cluster sampling
Each element has the same probability of being selected and each combination of elements has the same probability of being selected
Simple Random Sample
Selected directly from the sampling frame, without using random numbers. Selecting every “nth”
Systematic Sample
What is a potential problem with systematic sampling?
periodicity (occurs if the cases in the sampling frame are arranged in some systematic order) which affects representativeness
Used for large populations when there are no adequate sampling frame and elements are geographically dispersed
Multi-Stage Cluster Sampling
Ensures that subgroups in the population are proportionally represented in the sample by stratifying the population and selecting a simple random sample or a systematic sample from each stratum.
Stratified Random Sampling
standard error of the mean
about 95 percent of all sample means lie within 1.96 standard errors off the mean.
the greater the heterogeneity of the population on the characteristics of interest…
…the larger the sample size should be
Types of Non-Probability Sampling (3)
Convenience sampling
Snowball sampling
Quota sampling
Typically used in qualitative research
Cases are included because they are readily available
Convenience Sampling
