Statistics Flashcards
Define population
A set of items that are of interest
Define census
A measure of every member of a population
What is meant by a sampling unit?
A selection of the population used to estimate information about the population as a whole
Give an advantage of a census
Completely accurate result
Give 3 advantages of a sample
- Less time-consuming
- Fewer responses needed
- Less data to process
Give 3 disadvantages of a census
- Time consuming
- Cannot be used if the sampling process would render the items unusable
- Processing a lot of data takes a long time
Give 2 disadvantages of a sample
- Data might not be accurate
- Sample might not be properly representative of the population
Describe simple random sampling
Selecting members will involve assigning numbers to all members of the set, and generating numbers at random to choose them
Describe systematic sampling
members are chosen at regular intervals from an ordered list
Describe stratified sampling
Dividing the population into groups and randomly choosing the same number from each group
Give 3 advantages of simple random sampling
- Free of bias
- Easy and cheap to implement
- Every unit has an equal chance of selection
Give 2 advantages of systematic sampling
- Simple and quick to use
- Suitable for large samples and populations
Give 2 advantages of stratified sampling
- Sample accurately reflects the population
- Guarantees proportional representation of groups
Give 3 disadvantages of simple random sampling
- Not suitable for a large population or sample size
- A sampling frame is needed
Give 2 disadvantages of systematic sampling
- A sampling frame is needed
- Possible bias as units do not have an equal chance of selection
Give 2 disadvantages of stratified sampling
- Population must be classified into groups which can be time-consuming
- Selection within a group has the same issues as simple random sampling
Give the 2 types of non-random sampling
- Quota
- Opportunity
What is quota sampling?
Where an interviewer or researcher selects a sample that reflects the characteristics of the group
What is opportunity sampling?
Where the sample is taken from people available at the time and who fit the criteria needed
Give 3 advantages of quota sampling
- Allows a small sample to represent the population
- No sampling frame required
- Quick and inexpensive
Allows comparison between groups
Give 4 disadvantages of quota sampling
- Potential for bias to be introduced
- Can take time to divide the population into groups after
- A more in-depth study would require an increasing number of different groups
- Some people might not be willing to take part
Give 2 advantages of opportunity sampling
- Easy to carry out
- Inexpensive
Give 3 disadvantages of opportunity sampling
- Unlikely to give a proportional sample
- Researcher’s ability can affect the outcome
- People might not want to be interviewed/asked
Define quantitative data
Data which is numerical
Define qualitative data
Data which is non-numerical
What is discrete data?
Data which can only take certain values
What’s continuous data?
Data which can take any value
What are class boundaries?
maximum and minimum values that belong in a group
What is the classwidth
the difference between the upper and lower class boundaries
