sampling Flashcards
what is a random sample
where each strand of the population has an equal chance of being selected
what is a simple random sample
a random sample without replacement
what are three advantages of simple random smapleing
- free from bias
- each to implement
- each sample strand has an equal chance of selection
what are three disadvantages of simple random sampling
- not suitable with a large population size
-a sampling frame is needed
what is a sampling frame
a collection of all the sampling units, this could be a list of the whole population labelled with unique identities e.g. names. often is impractical
sampling unit - define
an indivdual member of the population that can be sampled
what is systematic sampling
gathering your sample in a systematic way - for example every 5th person from a ist of names
how to gather n in a systematic sample
decide how large you want your sample size to be. dividre that number by the population size. every nth number is the subject who is to be in the sample size group.
what are some advantages of systematic sampling
- simple and quick to use
- suitable for large populations and samples
what are some disadvantages of systematic samples
a sampling frame is needed
– can lead to bias if the sampling frame is not random
what is a stratifeid sampling
where a strata is taken that is rerpresentIVE OF THE POPULATION
what are some advantages of stratified sampling
sample accurately reflects the population structure
- guarantees proportional representation
what are some disadvantages of stratified sampling
population must clearly be classified into distinct strata ( this can be time consuming)
- sampling frame is needed
what is opportunity sampling
uses strands of the population that area available there and then
what are advantages of opportunity sampling
- cheap - easy
