Sampling Flashcards
What is simple random sampling?
A simple random sample of size n is one where every sample of size n has an equal chance of being selected.
What is required for simple random sampling?
A sampling frame eg a list
What are the two methods for choosing numbers in simple random sampling?
Generating random numbers using a calculator.
Lottery sampling eg choosing tickets out of a hat.
What is systematic sampling?
The required elements are chosen at regular intervals from an ordered list.
What is stratified sampling?
Population is divided into two mutually exclusive strata eg males and females, and a sample is taken from each.
What is the formula to calculate the the number of people we should sample from each stratum?
number in stratum/number in a population x overall sample size
What are the advantages of simple random sampling?
Free of bias
Easy and cheap to implement
Each sampling unit has a known and equal chance of selection.
What are the advantages of systematic sampling?
Simple and quick to use.
Suitable for large samples/populations
What are the advantages of stratified sampling ?
Sample accurately reflects the population structure.
Guarantees proportional representation of groups within a population.
What are the disadvantages of systematic sampling?
A sampling frame is needed.
It can introduce bias if the sampling frame is not random.
What are the disadvantages of stratified sampling?
Population must be clearly classified into distinct strata.
What are the disadvantages of simple random sampling?
Sample frame needed.
Not suitable when population size is too large.
