Data Collection Flashcards
What is the advantage of census?
A completely accurate result
What is the disadvantage of census?
- Time consuming and expensive
- Cannot be used during testing as destroys the item
What is the advantage of sample?
- fewer people have to respond
- less time consuming and expensive than census
What is the disadvantage of a sample?
- may not be as accurate
- sample might not be large enough to give info on sub-groups
What are sampling units?
individual units of a population
What is simple random sampling?
Every sampling unit is assigned a number and randomly picked
What is systematic sampling?
The required number of sampling units are picked at regular intervals. First number is picked at random
What is stratified sampling?
Population is divided up into mutually exclusive strata and a random sample is taken from each
How do you calculate number sampled in a stratum?
number in stratum / * overall sample size
number in population
What are the advantages of simple random sampling?
- free of bias
- easy and cheap for small populations
What are the disadvantages of simple random sampling?
- not suitable for large populations as time consuming
- a sampling frame is needed
What are the advantages of systematic sampling?
- simple and quick
- suitable for large populations
What are the disadvantages of systematic sampling?
- sampling frame needed
- introduce bias if frame isn’t random
What are the advantages to stratified sampling?
- accurately represents population structure
- guarantees proportional representation
What are the disadvantages of stratified sampling?
- population must be classified into strata
