DATA COLLECTION Flashcards
What is a population?
A whole set of items that are of interest.
What is a census?
When information about every member of the population is collected
What are the advantages of a census?
Should be completely accurate
What are the disadvantages of a census?
-Time consuming/expensive
-Hard to process large quantity data
What are the advantages of a sample?
-less time consuming and cheaper
-Fewer people have to respond
-less data needs to be processed
What are the disadvantages of a sample?
-Data may not be as accurate
-sample not large enough to give info about subgroups of the population.
What is random sampling?
where every sample of size n has an equal chance of being selected.
What are the advantages of random sampling?
-Free of bias
-easy and cheap for small samples
-each sampling unit has a known and equal chance of selection
What are the disadvantages of random sampling?
-not suitable for large samples and populations
-sampling frame needed
What is systematic sampling?
Sample is formed by choosing members of a population at regular intervals using a list.
What are the advantages of systematic sampling?
-simple and quick to use
-suitable for large samples/populations
What are the disadvantages of systematic sampling?
-sampling frame is needed
-A bias is introduced if sampling frame is not random.
What is stratified sampling?
When the population is divided into mutually exclusive strata and a random sample is taken from each.
What are the advantages of a stratified sample?
-accurately reflects population structure
-proportional representation of group within population.
What are the disadvantages of a stratified sample?
-population must be clearly classified into distinct strata.
-not suitable for large samples
-sampling frames needed
What is quota sampling?
selected sample reflects the characteristics of the whole population.
What are the advantages of quota sampling?
-representative of population
-no sampling frame needed
-quick, easy, inexpensive
What are the disadvantages of quota sampling?
-non-random sampling could introduce bias
-population must be divide into groups so not accurate
What is opportunity sampling?
Sample taken from people who are available at the time of the study
What are the advantages of opportunity sampling?
-easy and inexpensive
What are the disadvantages of opportunity sampling?
-unlikely to provide a representative result
