RM: Sampling Flashcards
(17 cards)
What is an opportunity sample?
Recruit those who are most convenient or most available to you. e.g. students at your school.
What is a random sample?
Use a random technique e.g. a random number generator.
What is a stratified sample?
Identify relevant subgroups, randomly select appropriate proportion from each subgroup- using a random technique.
What is a systematic sample?
Using a predetermined system to select participants. e.g. selecting every 6th, 14th or 20th person from a phonebook!
What is a volunteer sample?
When people respond to an advertisement!
Opportunity sample- strengths
- The easiest method because you just use the first suitable participants you can find- which means it takes less time to locate your sample than if you use other techniques!
Random sample- strength
- Unbiased; all members of the target population have an equal chance of selection.
Stratified sample- advantages
Likely to be more representative than other methods because there is a proportional and randomly selected representation of subgroups.
Systematic sample- advantages.
Unbiased as participants are selected using an objective system.
Volunteer sample- advantages
- Gives access to a variety of participants (e.g. all the people who read a particular newspaper) which may make the sample more representative and less biased!
Disadvantages- opportunity sample
Inevitably biased because the sample is drawn from a small part of the population!
e.g. If you selected your sample from people walking around the centre of town on a monday morning- it would be unlikely to include professional people (because they are at work) or people from rural areas!
Disadvantages- random sample
Need to have a list of all members of the population and then contact all of those selected- may be time consuming!
Stratified sample- disadvantage
Very time consuming to identify subgroups, then randomly select participants and contact them!
Systematic sample- disadvantage
Not truly biased/ random unless you select a number using a random method and start with this person- and then select every nth person!
Volunteer sample- disadvantage
- Sample biased in other ways- participants are likely to be more highly motivated and/ or with extra time on their hands.
- They might be more highly motivated to be helpful, or more broke and needing the money offered for participation. This results in volunteer bias.
What does bias mean?
A systematic distortion!
What is generalisation?
Applying the findings of a particular study to the population.
