Stage 2 Flashcards
What is primary data?
Original data that has not been previously collected/processed. All data is collected first hand.
What is secondary data?
Data from published sources which have been processed/analysed.
What is sampling?
Sampling is a sub-set of items taken from the whole population (all of the data available).
What is random sampling?
Where each individual is chose randomly and by chance.
What are the advantages of random sampling? (2)
- Least biased way of sampling because every individual has equal chance of being selected.
- Quick and easy.
What are the disadvantages of random sampling? (2)
- Theoretically the same individual could be selected more than once.
- May not take samples from whole sample area.
What is stage 2?
Developing a strategy
What is systematic sampling?
Selection of data from an ordered sampling frame. (Samples are evenly spaced e.g. Every 100m along a transect)
What are the advantages of systematic sampling? (3)
- Quick and easy.
- Samples taken from all parts of the area so whole area is covered.
- No individuals selected more than once.
What are the disadvantages of systematic sampling? (1)
The regular interval may miss an important variation.
What is stratified sampling?
Taking different sub-section samples e.g. Sampling different year groups separately within a whole school population.
What are the advantages of stratified sampling? (1)
Variations are sampled.
What are the disadvantages of stratified sampling? (1)
Can introduce bias because researchers select predetermined factors as being important e.g. Land use or age/gender of population.
What is pragmatic sampling?
Samples are taken from areas which are safe or accessible.
What are the advantages of pragmatic sampling? (2)
- Practical, quick and easy method.
- Safe
