Chapter 1 - Data Collection Flashcards
(27 cards)
Population
whole set of items that are of interest
Census
observes or measures every member of a population
Sample
is a selection from a subset of the population to find out information about the population as a whole
Advantages of a Census
gives a complete accurate result
Disadvantages of a Census
- Time consuming
- Expensive
- Harder to process large quantities of data
Advantages of a Sample
- Less time consuming and expensive than a census
- Fewer people
- less data to process
Sampling Units
Individual units of a population
Sampling frame
List of the sampling units
Simple random sampling
every sample has an equal chance of being selected
How to conduct a simple random sample?
1) Identify a sampling frame
2) Allocate each person a unique number
3) Then a selection of these numbers is chosen at random by a number generator
Systematic Sampling
The samples are chosen at regular intervals from an ordered list
How to conduct a systematic sample
1)Take the population and divide by the sample to workout the interval.
2) the first person should be chosen at random
Stratified sampling
The population is divided into mutally exclusive strata
How to conduct a stratified sample
1) the proportion of each strata sampled should be the same
2) Number sampled = Number in strata/Number in population x Overall sample size
Advantages of Simple random sampling
- free of bias
- Easy + cheap
- Fair as equal chance of selection
Disadvantages of simple random sampling
- `not suitable if too large
- Sampling frame is needed
Advantages of systematic sampling
- Simple & Quick to use
- Suitable for large populations
Disadvantages of systematic sampling
- a sampling frame is needed
- can introduce bias
Advantages of stratified sampling
- Sample accuratley reflects the population
- Proportional representation
Disadvantages of stratified sampling
- population must be clearly classified
- sampling frame is needed
Quota sampling
a researcher selects a sample that reflects the characteristics of the whole population
Opportunity Sampling
Taking a sample from people who are available at the time the study is carried out and fit the criteria
Advantages of quota Sampling
- Allows a small sample to be representative
- No sampling frame
- quick easy and inexpensive
- allows for easy comparisons
Disadvantages of Quota Samplig
- Can introduce bias
- Population must be divided into groups
- Time consuming
- Non-Responses are not recorded
