Data Collection Flashcards
Define population
The whole set of items that are of interest
Define sample
A selection of observations taken from a subset of the population which is used to find out information about the population as a whole
Define sampling frame
Sampling units of a population are individually named or numbered to form a list called a sampling frame
Define sampling unit
Individual units of population
Define census
A census observes or measures every member of a population
What are the advantages of a census
It should give a completely accurate result
What are the disadvantages of a census
- Time consuming and expensive
- Cannot be used when the testing process destroys the item
- Hard to process large quantity of data
What are the advantages of a sample
- Less time consuming and expensive than a census
- Fewer people have to respond
- Less data to process than in a census
What are the three sampling methods
- Simple random sampling
- Systematic sampling
- stratified sampling
Define simple random sample
A simple random sample of size n is one where every sample of size n has an equal chance of being selected
What are the two ways of carrying out a simple random sample
Lottery sampling -> writing numbers on tickets and drawing out of a hat
Sampling frame -> each person / list is allocated a unique number. Selection of these numbers is chosen at random
What are the advantages of systematic sampling
- simple and quick to use
- suitable for large samples and large populations
What are the disadvantages of systematic sampling
- a sampling frame is needed
- it can introduce bias if the sampling frame is not random
Define systematic sampling
the required elements are chosen at regular intervals from an ordered list
What are the advantages of simple random sampling
Free of bias
Easy and cheap to implement for small populations and small samples
Each sampling unit has a known and equal chance of selection
What are the disadvantages of simple random sampling
Not suitable when the population size or the sample size is large
A sampling frame is needed
Define stratified sampling
the population is divided into mutually exclusive strata (males and females e.g) and a random sample is taken from each
Define quota sampling
The interviewer or researcher selects a sample that reflects the characteristics of the whole population
What are the advantages of quota sampling
Allows a small sample to still be representative of the population
No sampling frame required
Quick, easy and inexpensive
Allows for easy comparison between different groups within a population
What are the disadvantages of quota sampling
Non-random sampling can introduce bias
Population must be divided into groups, which can be costly or inaccurate
Increasing scope of study increases number of groups, which adds time and expense
Non-responses are not recorded as such
Define opportunity sampling
Taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for
What are the advantages of opportunity sampling
Easy to carry out
Inexpensive
What are the disadvantages of opportunity sampling
Unlikely to provide a representative sample
Highly dependent on individual researcher
