Sampling Flashcards
Define what a population is.
Group which is the focus of the researcher, from which a smaller sample is drawn
Define what a sample is.
Group of people who take part in an experiment.
Drawn from a target population and presumed to be representative of that population.
Define sampling technique.
Method used to select people from a population.
Define bias in the context of sampling.
When certain groups are over/under represented within the sample.
E.g. too many youngsters - limits generalisation
Define generalisation.
Extent to which findings and conclusions from an experiment can be applied to the broader population.
This is possible if the sample is representative of the population.
What is a random sample?
How is it carried out?
Form of sampling where all participants are equally likely to be picked.
- Make a list of all participants
- Assign a number to each name
- Choose the sample through a lottery method - put all numbers in hat and choose or put into a computer random number generator
What is a systematic sample?
How is it carried out?
When every nth participant is selected.
- Create a sampling frame where participants are organized, e.g. by alphabet
- Randomly choose interval to prevent bias
- Work through sample frame until sample is complete
What is a stratified sample?
How is it carried out?
Composition of sample reflects strata (sub-groups) of the target population.
- Identify the strata in the population
- Work out proportions needed for sample
What is an opportunity sample?
How is it carried out?
Anyone is selected who’s willing and available.
• Researcher asks whoever is around at the time
What is a volunteer sample?
How is it carried out?
Participants are self-selected.
- Researcher gains participants through a newspaper advert
- PPs simply raise hands when researcher asks.
Evaluate random sampling.
Strengths:
+ No researcher bias: researcher has no influence over who is selected
Weakness:
- Difficult and time-consuming
- Sample may still not be representative of target population - still a chance a similar profile of person is chosen in the sample
- Selected participants may refuse to take part so could end up with slightly volunteered sample
Evaluate systematic sampling.
Strengths:
+ No researcher bias: Once system for selection is established, researcher has no influence over who’s chosen
+ Fairly representative - possible but very unlikely selected participants will be similar to each other
Weakness:
- Selected participants may refuse to take part so could end up with slightly volunteered sample
Evaluate stratified sampling.
Strength:
+No researcher bias: Once target population is divided into strata, PPs are randomly selected so researcher has no influence
+ Representative sample bc it’s designed to reflect the composition in the population - so can generalise findings
Weakness:
- Strata don’t reflect all the differences between people so complete representation of population isn’t possible
Evaluate opportunity sampling.
Strength:
+ Convenient - saves researcher time and effort and cheaper than other sampling methods
Weakness:
- Sample is unrepresentative of target population as it’s made from a specific area, e.g. one street in one town, so can’t generalise findings
- Researcher bias - researcher chooses participants which will be based on the researcher’s own personality
Evaluate volunteer sampling.
Strength:
+ Easy to conduct
+ Requires minimal input from researcher, so less time consuming than other sampling methods
Weakness:
- Volunteer bias - asking for volunteers may attract a specific profile of person e.g. one that is helpful and curious. Due to this, findings will lack generalisability.
