Question | Answer |
Selection of Pps and sampling techniques- including random, opportunity and volunteer sampling | -when conducting research, psychologists need Pps. -in an ideal world, a study would include all members of a target population as this would provide the most accurate results. |
A target population | -this is a group of people who share the same characteristics about which a researcher wishes to draw conclusions e.g. married women, A level students, males over the age of 40 who enjoy playing golf. -clearly it is impossible to include all members of the target population within a study so a selection of that population, a sample is included instead. -if a sample is truly representative, then psychologists should be able to generalise the conclusions of the study to the whole target population. |
Sample | -samples can be selected in several different ways -a part of a population selected such that it is considered to be representative of the population as a whole. -3 ways 1. random sampling 2. opportunity sampling 3. volunteer sampling |
Representative sample | -the notion that the sample is representative of the whole population from which it is drawn. |
Generalisability | -the extent to which the findings of a study can be applied to other settings, populations, time and measures. |
3 sampling techniques | -the most obvious way to gain a sample is to use the people who happen to be around at the time (called an opportunity sample). -most psychologists use this method or a volunteer sample. -the 'ideal' method is a random sample because it is the least biased. |
Random sampling | EXPLANATION -selecting Pps on some random basis (e.g. picking numbers out of a hat) -every member of the population has an equal chance of being selected. -it involves selecting Pps in a highly organised way using randomisation techniques. ADVANTAGE 1- it has high population validity because it is normally a representative sample. ADVANTAGE 2- This is a representative sample (usually) DISADVANTAGE 1- selecting a random sample does not guarantee a sample that is totally representative of the population concerned. -however, as long as the target population and sample size have been chosen carefully, the laws of probability predict the chance of selecting a biased sample is minimal. DISADVANTAGE 2- time consuming- it takes a lot of time and effort to conduct a study using random sampling. -inconvenient and hard -researchers don't like to do this |
Volunteer sampling | EXPLANATION - choosing research Pps who have volunteered, -e.g. by replying to an advertisement -volunteer samples may not be representative of the general population, which means the research may not be generalisable ADVANTAGE 1- it is fairly easy to gather Pps together ADVANTAGE 2- allows researchers to find out things that are sensitive and that only apply to the minority (specific topics) DISADVANTAGE 1- the majority of a given target population are unlikely to respond to the request the participate, and those who do respond (i.e. volunteers) may not be typical of the target population in some way. DISADVANTAGE 2- low population validity -potentially biased sample -unlikely to be representative of the target population -findings of the study cannot be generalised people likely to take part (volunteering) -unemployed people who have time -students -confident persons -outgoing -these people can't be generalised-they are specific groups of people =very unrepresentative |
Opportunity sampling | EXPLANATION - Pps are selected because they are available, not because they are representative of a population ADVANTAGE 1- fast and not very time consuming= most common type of sampling used ADVANTAGE 2- easy method to use out of all 3 sampling methods as it is quick and convenient DISADVANTAGE 1- unlikely to generate a sample that is representative of the wider target population from which it is drawn. =not representative DISADVANTAGE 2- findings of the study can't be generalised -low population validity |
what to remember in test for sampling methods | 1. difference between the 3 methods 2. high/low population validity 3. sample/target population 4. representative or not? |
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