Sampling Methods Flashcards
How we select participants for a study (tehniques + evaluations) (17 cards)
What is sampling?
SELCTING participants to take part in our study from the target population (as we can not test everyone)
How should the sample pop represent the target pop?
Sample pop should be representative of target pop so we can generalise the findings to the rest of tatger pop without studying them all.
What is sampling bias?
It may occur if the sample that is selcted is not representative of the rest of the population.
To avoid it, try making sample size as large as possible.
What is the target population?
The population the study is aimed to apply to.
What is the sample population?
The selected group from the target population that are actually tested.
What is random sampling?
EVERY member of target pop has an equal chance of being chosen.
. Identify everyone in target pop and how many ppt you need, and then giving everyone an equal chance of being picked.
example: draw names out of a hat.
What are the strenghts of random sampling?
. NO RESEARCHER BIAS: eliminates possibility of researchers bias, as they have no say in who takes part. Increases validity as the results are more accurate (equal chance of being chosen).
. MORE REPRESENTATIVE SAMPLE: everyone has equal chance of being chosen, meaning wider variety of people being chosen- higher change of generalising results accurately. Increases validity as more ppl that can be chosen more representative of target pop.
What are the weaknesses of random sampling?
. TIME CONSUMING: having to select randomly, means more time taken to write their names down and randomly select (esp since large sample size needed). Less time efficient, compared to other methods.
. STILL BE UNPREPRESENTATIVE: due to time consuming, researcher may have smaller sample size (and more similar ppl picked). for example, more males can be picked from hat- not representative. Decreases validity, as we cannot guarantee that a generalisable population can be picked.
What is opportunity sampling?
Most used by psychology students.
Taking sample population from those who are avaliable at the time and fit our criteria (etc taking a year 7 class)
Strenghts of opportunity sampling?
QUICKER AND EASIER: due to selection people who are available, much quicker process… as it is more convient. Adds to validity as it is more time efficient and we can get a larger sample.
Weakness of opporunity sampling?
LESS LIKELY TO BE REPRESENTATIVE: due to selecting those who are avaliable at the time, may get similar kinds of people. eg: if you go to a carrefour during lunchtime, lots of students available. time and location may limit types of people selected which decreases validity as cannot ensure representatie sample.
RESEARCHER BIAS: due to researcher picking pop based on convience they can subconciously choose people they think will do better (eg could be drawn to more athletic people). Decreases validity as there is bias in the pop and therefore invalid results.
What is volunteer sampling?
Participants becoming the sample pop becuase they volunteered in response to an advert or flyer etc.
Strenghts of volunteer sampling?
QUICKER/EASIER: participants volunteering thesmelevs, quicker sample obtained. Adds to suitability of this sampling as easier to conduct and more efficient.
NO RESEARCHER BIAS: they have to accept the people that have volunteered, which reduces the research bias. adds to validity as more representative population.
Weaknesses of volunteer sampling?
. LESS REPRESENTATIVE AS WELL: only certain types of people will take part (eg those who have spare time, or are more interested inrstudies, or unemployed, studies). questions vlidity, as findings not fully generalised to the target population (only certain people volunteer).
What is stratified sampling?
Identifying all the sub groups (strata) in the target population.
For example if my target population is all of Dubcoll, i would figure out the % of staff, and the % of students.
I would then use the SAME percentages in my sample population, to ensure it reflects the larger proportions.
Strenghts of stratified sampling?
MOST REPRESENTATIVE:
. Means whole target population will be represented well, as specific percentages mean that it will represent properly and can be generlised. Increased validity, as representative findings and matches target pop really well.
NO RESEARCHER BIAS:
Researcher has no input in who is chosen, as they have to choose with the percentage (and can improve further by randomising who they pick from that percentage). Can be generslised to whole target population, which increases validity as results more accurate/representative.
Weakness of stratified sampling?
Time consuming and difficult to carry out.
have to work out exact percentages and then choose names randomly from that percentage, it is time consuming and many steps taken- with some researches even taking short cuts (reducing validity as it is not time efficinet enoug compared to other methods).
