Chapter 1 - Data Collection Flashcards
Define population:
The entire set of items of interest
Define census:
When data is collected from every member of a population
Define sample:
A set of observations taken from a subset of the population
Advantages of a census:
Completely representative
Disadvantages of a census:
Time consuming, expensive and can’t be used if the item needs to be destroyed in the testing process
Advantages of a sample:
Cheaper, quicker, less data to process
Disadvantages of a sample:
May be less accurate, may not be enough to give info about small subsets of a population
Define sampling unit:
An individual in the population
Define sampling frame:
An ordered list of sampling units
What is a simple random sample:
The number of sample units needed are randomly selected from the entire population
What is systematic sampling:
When every nth sampling unit is selected from a random starting point
What is stratified sampling:
The population is divided into mutually exclusive strata and a proportionate number of sampling units are randomly selected from each
How to calculate the sample size for a strata:
(Strata size/population size) * sample size
Advantages of simple random sampling:
Bias free, easy, cheap, everyone gets an equal chance
Disadvantages of simple random sampling:
Needs a sampling frame, not suitable for large populations as it gets expensive and time-consuming
Advantages of systematic sampling:
Easy, quick, good for large populations
Disadvantages of systematic sampling:
Needs a sampling frame, can introduce bias
Advantages of stratified sampling:
Accurately reflects population structure, guarantees proportional representation
Disadvantages of stratified sampling:
Population needs to be classified, same issues as simple random within the strata
What is opportunity/convenience sampling:
Collecting data from the first sampling units you find
What is quota sampling:
Opportunity sampling, but according to different quotas so there’s proportional representation
Advantages of quota sampling:
A small sample can still be representative, no sampling frame, quick, easy, cheap, allows for easy comparison
Disadvantages of quota sampling:
Can introduce bias, population needs to be classified
Advantages of opportunity/convenience sampling:
Easy, cheap
Disadvantages of opportunity/convenience sampling:
Unlikely to be representative, depends on individual researcher
What is a discrete variable:
Non-continuous, like colour or number of people
