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sampling techniques - Coggle Diagram
sampling techniques
opportunity
+quick and easy method of gaining ppts because the researcher is choosing who is available at the time unlike stratified sampling which requires each strata to be identified then ppts selected at random
+appropriate to use when the sampling frame is unknown- such as people in a shopping centre. it is impossible to use some other sampling techniques such as random or stratified when you don't know who will be there at the time
-is likely to result in a biased sample as it is drawn from a small section of the population who are at the same place at the same time and are likely to share similar characteristics e.g. students who use the common room. therefore, it will be unrepresentative and unlike a stratified sample which selects from across the sampling frame
-increased chance of researcher bias as they may only approach ppts who they think fit their aims/hypothesis lowering the internal validity unlike random sampling which gives everyone an equal chance of being selected
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stratified
-very time consuming as all the subgroups have to be identified and then selected at random unlike self selected where ppts come forward themselves to take part in research
-even though this technique will select the most representative sample group of the population compared to other techniques, it is still likely there will be some bias as not all subgroups or strata can be identified
+most representative sampling method as there is a proportional representation of subgroups therefore findings can be generalised to the target population
+compared to an opportunity sampling there is less chance of researcher bias as the random technique e.g. using random number generator, chooses participants rather than the researcher themselves
subgroups or strata within a target population are identified (e.g. boys and girls or age groups). ppts are gained from each strata in proportion to the rate they appear in the target population. then selection from the strata is done using a random technique
self-selected
advertise for ppts in a newspaper, on a notice board or the internet. ppts then volunteer to take part
+seen to be more ethical than other sampling techniques as you are surer you have ppts consent as they have volunteered for the study unlike random sampling where ppts may feel obliged to take part as they have been selected
+quick and easy method of gaining ppts because the researcher has to place the advert then wait for ppts to volunteer unlike stratified sampling which is very time consuming as it requires each strata to be identified then ppts selected at random
-prone to volunteer bias as it may result in a biased sample as it may be that only certain types of people are likely to volunteer e.g. extroverts or highly motivated people. therefore, the sample may be unrepresentative making it difficult to generalise findings to the target population -compared to other sampling techniques you may be more likely to get demand characteristics as volunteer are more eager to help the researcher find evidence to support their aims
random
+unbiased as everyone in the target population has an equal chance of being selected meaning the sample should be more representative and findings more generalisable to the target population than opportunity samples
+compared to an opportunity sampling there is less chance of researcher bias as the random selection technique e.g. names in a hat, chooses the participants rather than the researcher themselves
-time consuming as the researcher must identify everyone in the target population and select ppts at random unlike opportunity sampling which is quick and easy
-still may result in a biased sample- it is possible that the random selection may result in a 'freak' unrepresentative sample unlike stratified which selects ppts from each strata in proportion to the rate they appear in the target population
get a list of all the people in the target population. write all the names on pieces of paper then place into a hat, select the number of ppts you require from the hat. OR enter names of people in target population into a computer random number generator. click the button**times to get the number of ppts needed
snowball
+useful at gaining access to difficult to reach ppts for example people with addictions meaning it may be the most appropriate technique for gaining ppts to research some behaviours
+appropriate when the sampling frame is unknown
-unlikely to be representative as it uses friends/contacts of initial ppts meaning it may be difficult to generalise the findings as they will be from similar groups
-more time consuming compared to opportunity sampling technique as the researcher needs to wait for ppts to refer other participants
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systematic
+less chance of bias as ppts are selected using an objective system e.g. every 10th person meaning unlike opportunity sampling where the researcher may approach ppts who suit their aims +quicker sampling technique than stratified sampling as you do not need to establish the proportions of different groups within the population
-still may result in a biased sample- it is possible that the system may result in a 'freak' unrepresentative sample unlike stratified which selects ppts from each strata in proportion to the rate they appear in the target population
-not practical when the sampling frame is unknown, such as drug addicts, where a snowball of volunteer sample may be more appropriate
use a pre-determined system (e.g. every 14th or 20th person) to select every nth ppt from the target population
quota
+most representative sampling method as there is a proportional representation of subgroups therefore findings can be generalised to the target population
+quicker than using a stratified sampling technique
-very time consuming as all the subgroups have to be identified and then selected unlike self-selected where ppts come forward themselves to take part in research -may still contain an element of researcher bias as a non-random technique is used to select the participants in each quota- the researcher may identify participants in each quota that may support their hypothesis
subgroups or strata within a target population are identified (e.g. boys and girls or age groups) ppts are gained from pre-set numbers from each of the strata. then selection is done using a non-random technique