5.sampling Flashcards
What is a population ?
A group of people who are the focus of the researchers interest
What is a sample ?
A group of people drawn from a target population who take part in a research investigation
What is a target population ?
The target population is the total group of individuals from which the sample might be drawn.
What is bias in the context of sampling ?
Bias refers to when certain groups may be over or under represented within the sample
What is generalisation ?
The extent to which findings and conclusions from a certain investigation can be broadly applied to the population
What is a random sample ?
All members of the target population have an equal chance of being selected for the sample
What is the method for a random sample ?
- Complete list of all members of the target population
- Assign all names on the list a number
- Sample is generated through the use of a lottery method
What is a stratified sample ?
The sample reflects the proportions of people in certain strata within the target population
How do you carry out a stratified sample ?
- Identifies the different strata that make up the population
- Work out the proportions needed for the sample to be representative
- Participants that make up each stratum are selected using random sampling
What is an opportunity sample ?
When the researcher selects anyone who happens to be willing and available.
How do you carry out an opportunity sample ?
The researcher takes the chance to ask whoever is around at the time of their study
What is a volunteer sample ?
Involves participants selecting themselves to be a part of the sample
How do you carry out a volunteer sample ?
A researcher may place an advert around where their target audience would be and people will volunteer.
What are the strengths of a random sample ? (2)
- free from research bias
- should be representative
What are the weaknesses of a random sample ? (3)
- difficult and time consuming
- may end up with a sample that is still unrepresentative
- selected participants may refuse to take part
What is the purpose of sampling ?
It is very difficult to study every single person in a target population
What is systematic sampling ?
When every nth member of the target population is selected
How do you carry out a systematic sample ?
- A sampling system is nominated e.g every 3rd person (May be randomly determined to reduce bias)
- The researcher then works through the sampling frame until the sample is complete
What are the strengths of a systematic sample ? (2)
- avoids researcher bias
- fairly representative
What are the weaknesses of a systematic sample ? (3)
- could be unlucky to get an all male sample for example
- very difficult to achieve as it is time consuming, is expensive and requires a lot of effort
- selected participants may refuse to take part
What are the strengths of a stratified sample ? (2)
- avoids researcher bias
- representative
What are the weaknesses of a stratified sample ? (3)
- identified strata cannot reflect all the ways that people are different
- people may refuse to participate so they may be unable to make up each
- time consuming and requires a lot of effort
What are the strengths of an opportunity sample ?
- convenient, saves time and effort
What are the weaknesses of an opportunity sample ?
- unrepresentative as participants are drawn from a very specific area
- may be subject to researcher bias as they have complete control and get the selection of participants
