Sample and Sampling techniques Flashcards
What is a Sample?
1)The group of participants in a piece of research (study) are called the sample. When a psychologist conducts a piece of research they must think of the most suitable way of obtaining participants.
2)The psychologist must try and get a sample that is most representative of their target population (the group of people they want to be able to generalise their findings to).
E.g if I wanted to investigate 16-18yr olds’ level pf online socialising, my sample would be a selection of 16-18 year olds. SAMPLE SIZE can be important too as generally small samples will be less representative than larger samples.
What are the sampling techniques/methods that could be used?
Opportunity Sampling
Random Sampling
Snowball Sampling
Volunteer/Self-selecting Sample
What is opportunity sampling?
It’s the easiest and quickest method of sampling. It is simply about making use of the people who are readily available to you and who fit in the target population.
FOR EXAMPLE- if I was conducting the above study on internet socialising, as your teacher I could simply use you, my students, as participants.
What is random sampling?
The researcher needs the names of all members of his target population to do this. All potential participants are entered into a draw of some kind such as a random number generator and names are randomly selected until the desired number of participants is chosen, everyone has an equal chance of being chosen.
FOR EXAMPLE- if I wanted to just look at internet socialising of CNC students, I would access the students data base and use a random number generator to select a sample of students.
What is snowball sampling?
The researcher begins with one participant and then asks them to invite others (friend or collegue) who they then ask others etc. It’s generally used if the target population may be difficult to access or contact.
FOR EXAMPLE- a researcher investigating navigation, who needs a sample of bus drivers, starts with one they know, who asks one of their colleagues, who then asks another one and so on.
Volunteer/self-sampling
The psychologist will place an advert (this could be a poster, a flyer distribution, a TV advert, postal mail etc). People interested in the study would reply and the psychologist would filter the responses to collect a sample that reflected their target population
For example, if I was studying internet socialising, I could have put a poster up in college asking students to email me and used the first 50 16-18yr olds that responded.
Strengths and weaknesses of opportunity sampling
:) -Is the easiest and quickest way to obtain participants as the psychologists will use people they already have access to. Therefore, this is the most efficient and least costly sampling technique.
:( -The sample may not be representative as the sample is taken from whoever is available at the time, often from the researchers own social/cultural group. Therefore this limits the generalisability of the results to the target population.
Strengths and weaknesses of random sampling
:)-Least bias method of sampling as all members of the target population have equal chance of being selected. Therefore, results should be more generalizable.
:(-It is very difficult to conduct, especially with large target populations as you need to access information about all members of your target population. It would be very time consuming Eg you could not do this if a target population was males all age 20-31.
Strengths and weaknesses of snow-ball sampling
:)-Relatively easy to obtain because the researcher only needs to find the first few participants therefore it is a convenient way to find a sample of a particular kind of participant.
:(-Non representative sample as they are likely to be in similar ways other than any common characteristics needed for the study as they all know each other/ work at the same place etc. Therefore, this limits the generalisability of results.
Strengths and weaknesses of Volunteer/self-selected sample
:)-This method allows the researcher to reach a wide range of potential participants as many different people will see the advertisements and be able to respond. Therefore, this could generate a representative sample.
:(-It is a biased method, leading to a non-representative sample, as people tend not to respond unless they have a strong view to share or a motivation. Therefore this may limit generalisability.
