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
