Flashcards in Experimental Design Deck (22)
What are the 2 conditions in an experiment?
Experimental and control conditions
In an experiment, the researcher must decide how to split participants between the experimental and control groups, what are the 3 methods of doing this?
1. Independent groups
2. Repeated measures
3. Matched pps/pairs
What is independent groups?
Tests the two different conditions on two different groups of people - random allocation
What are the strengths and weaknesses of independent groups?
+Less chance of order effects, like learning or fatigue
+Can use the same stimulus material
+No order effects
-Less effective for controlling participant variables such as individual differences
-requires more pps
What is repeated measures?
The different conditions of the experiment are performed on the same group of people
What are the strengths and weaknesses of Repeated measures?
+Participant variables eliminates (Weakness of IG)
+Fewer pps need to be found (W of IG)
-Order effects, like fatigue and learning occur (S of IG)
-Demand characteristics due to more contact with researcher
-Cannot use same stimulus material due to order effects (S of IG)
What can be done to manipulate repeated measure in order to reduce order effects?
pps can be counter balanced - half do condition 1 then condition 2, the other half do 2 then 1
What does counter balancing repeated measures do and how do you do it?
+reduces order effects
half do condition 1 then condition 2, the other half do 2 then 1
What is matched pairs?
participants in one group are matched to participants in the other group for traits like age gender and ability - like twins!
What are the strengths and weaknesses of matched pairs?
+pps variation is reduced
+no order effects
-need more pps (than repeated measures)
What is a Pilot study?
A small scale replication of a study - they are carried out to check the design and implementation of the main study
The selection of participants must reflect the what?
What is a target population?
A group of people who share a given set of characteristics about which the researcher wishes to draw a conclusion e.g. A level students
As the target population is normally too large, what does the researcher need to obtain?
A representative sample
What must the people in a representative sample posses?
Similar characteristics to the target population
What are the 3 methods of participant sampling?
What is opportunity sampling?
Most easily available
Biased because its drawn from a small section of the population
relies on people responding to adverts etc
Biased because it only attracts those from areas of advert - e.g. those who read the same type of newspaper/magazine
What is random sampling?
Produces the ideal sample because every member of the target population has an equal chance of being picked to be in the sample
What are observational studies?
are investigations where the researcher observes a situation and records what happens but does not manipulate an independent variable.
Observational studies therefore tend to be high in ecological validity as there is no intervention and if the observer remains undetected the method avoids problems with demand characteristics.
(Observational designs) What are time interval, time point and event sampling?
Time interval sampling: breaking down the observation into small, equally sized, time intervals and judging whether the operationalized behaviour occurs during each interval.
Time point sampling: involves selecting specific "points" at which to collect specific data. Information about those points can then be used to say something about a phenomena over a broader area.
Event sampling: Event sampling consists of the researcher recoding an event every time it happens. For example, ticking a box every time somebody picks their nose. Although behaviours should not be missed as in time sampling, if too many observations happen at once it may be difficult to record everything.