Statistics Flashcards
Define Qualitative
Data that is descriptive - uses words
Define Discrete Quantitative
Data that can be counted (number of plants in a field)
Define Continuous Quantitative
Data that can be measured (height of plant - ongoing)
Define Population
All the individuals you are interested in for a particular investigation
Define Census
Collecting data from the whole population
Advantages of a census
Should be completely accurate
Disadvantages of a census
- Time consuming
- Expensive
- Hard to process large quantity of data
Define Sample
Collecting data from part of the population
Advantages of sample
- Quick
- Cheap
- Less data to process
Disadvantages of sample
- Data may not be accurate
- Sample may not be large enough to give information about small sub-groups of the population
Define Simple Random Sampling
Every member of the population has an equal chance of being picked
Simple Random Sampling pros and cons
Pros: - Free of Bias - Easy and cheap to implement for small populations Cons: - Not suitable for a large sample size - A sampling frame is needed
Define Systematic Sampling
The required elements are chosen at regular intervals from an ordered list
Systematic Sampling pros and cons
Pros: - Simple and quick to use - Suitable for large samples and large populations Cons: - A sampling frame is needed - Can introduce bias
Define Stratified Sampling
Population divided into groups based on age, gender, etc. and a random sample is taken from each
Stratified Sampling pros and cons
Pros:
- Accurately reflects the population structure
- Guarantees proportional representation of groups within population
Cons:
- Population must be clearly classified into distinct strata
Define Quota Sampling
The researcher selects a sample that reflects the characteristics of the whole population
Quota Sampling pros and cons
Pros:
- No sampling frame needed
- Quick, easy and cheap
- Allows for easy comparison between different groups within a population
Cons:
- Could introduce bias
- Population must be clearly classified into distinct strata which can be inaccurate
Define opportunity sampling
Individuals chosen to be part of a sample as the opportunity arises
Opportunity Sampling pros and cons
Pros: - Easy to carry out - Inexpensive Cons: - Unlikely to provide a representative sample
Explain what is meant by stratified sampling and why it is used (4 marks)
- There are identifiable strata that may exhibit different characteristics
- Each stratum is randomly sampled
- Use it to obtain a representative sample
- Can use it to get information on the individual strata
