Data Collection Methods Flashcards
What are the 5 different data collection methods
- Simple Random Sampling
- Systematic Sampling
- Stratified
- Quota Sampling
- Opportunity/Convenience Sampling
What are the two non-random sampling techniques
- Quota
- Opportunity
How to carry out simple random sampling
Give each item in the sampling frame a unique number. Use a random number generater to select an amount of unique numbers
Advantages of simple random sampling
- Bias free
- Easy and cheap to implement
- Each number has an equal chance of being selected
Disadvantages of Simple Random Sampling
- Not suitible when population size is large
- Sampling frame needed
- Could get duplicate numbers
Population definition
The whole set of items that are of interest
Sample definition
A subset of the population that is inteneded to represent the population
Advantgaes of a census
Should give completely accurate results
Disadvantages of a Census
- Time consuming and expensive
- Can not be used when testing involved destruction
- Large volume of data to process
Advantages of a sample
- Cheap
- Quick
- Less data to process
Disadvantages of a sample
- Data may not be accurate
- Data may not be large enough to represent small sub-groups
How to carry out a systematic sample
Elements are chosen at regular intervals in an ordered list
i.e take every Kth element
k = Population size/Sample size
How to carry out a stratified sample
Population divided into groups (strata) and a simple random sample carried out in each group. Same proportion from each group. Samp size/pop size from each strata. Used when sample is large and can be divided into strata
Advantages of Stratified Sample
- Reflects population structure
- Garuntees proportional representation within groups of the population
Disadvantages of Stratified Sample
- Population must be clearly classified into distinct strata
- Selection within each stratum suffers from same disadvantags as simple random sampling
