1 - Data collection Flashcards
Define a population.
The whole set of items that are of interest.
Give 3 advantages of a sample.
- Less time consuming/expensive
- Fewer people have to respond
- Less data to process
Give two disadvantages of a sample.
- Data may not be as accurate
- Sample may not be large enough to give information about small sub-groups
Give three methods of random sampling.
- Simple random sampling
- Systematic sampling
- Stratified sampling
Give two ways of selecting numbers in simple random sampling.
- Random number generation
- Lottery sampling
How is stratified sampling undertaken?
- Population is divided into mutually exclusive strata.
- Random sample taken from each.
Give two methods of non-random sampling.
- Quota sampling
- Opportunity sampling
How does opportunity sampling work?
Taking the sample from people who are available at the time the study us carried out and fit the criteria you are looking for.
Define a discrete variable.
A variable which can only take specific values in a given range.
What is trace rainfall?
Amounts < 0.05mm
What is defined as moderate wind speed?
11-16 knots
What is daily maximum relative humidity measured in?
Percentage of air saturation with water vapour
What is daily mean cloud cover measured in?
Oktas - eights of sky covered by cloud
What is daily mean visibility measured in?
Decametres
What is daily mean pressure measured in?
Hectopascals
