Experimental Design and Statisitcs Flashcards
(52 cards)
Describe an Observational study
3 features
1) observe behaviour whilst it occurs naturally
2) descriptive method
3) can test hypotheses
What is a ‘variable’ ?
Any characteristic or factor that can vary
Issues with Observational studies (name 2)
OBSERVER BIAS - expectations of the observer & unconscious cues which influence the behaviour of P’s
REACTIVITY - change behaviour when we know we are being watched
How can we overcome issues with Observational studies?
OBSERVER BIAS
- code procedures
- make observers blind to hypothesis
- use several observers and rate their consistency
How can we overcome issues with Observational studies?
REACTIVITY
- use disguised observation for example two-way mirrors
- get P’s used to the observer
- use unobtrusive measures
What is a Correrlation study?
A relationship between two variables
Advantages of a Correlation study:
1) allows prediction
2) can study naturally occurring variables
Disadvantages of a Correlation study:
1) CANNOT establish a cause and effect relationship
2) third variable problem - unknown variable causing the change in the two variables rather than the variables themselves
What is an Experimental design?
- investigates the effect of an independent variable on a dependent variable
- variables are manipulated in a controlled setting
- all other conditions remain constant
What is the independent variable?
The variable that the experimenter manipulates
What is the dependent variable?
The variable that the experimenter measures
What is a ‘between subjects design’ ?
When participants are assigned to different experimental groups
INDEPENDENT MEASURES
eg one group of students is assigned to teaching method A whilst another group is assigned to teaching method B
Advantages of a between subjects design
- each P is naive to the experimental procedures
- essential when testing naturally occurring behaviours, eg gender
Disadvantages of a between subjects design
- large number of P’s needed for each experimental conditions
- individual differences eg personality traits
What is a “within subjects” design?
The same participants are tested under all the experimental conditions
REPEATED MEASURES
Advantages of a within subjects design
- fewer P’s needed
- no individual differences since the same P’s are used for each experimental condition
Disadvantages of a within subjects design
- order effects such as boredom or fatigue
* can stop this by using counterbalancing *
Define validity
Concerned with whether the method is measuring what it is supposed to be measuring
What is INTERNAL validity?
- deals with what is going on inside the study
- the extent to which an experiment supports a clear causal conclusion - is the IV causing the changes in the DV?
What factors limit internal validity?
1) confounding variables
2) expectancy effects
3) external validity
What are confounding variables?
An extraneous variable whose presence affects the variables being studied so the results you obtain do not actually reflect the actual relationship between the variables under investigation.
What are experimenter expectancy effects?
Subtle and unintentional cues which influence a P’s response
For example, an experimenter smiling when a participant behaves in the expected way
What are demand characteristics?
Cues that the participants pick up about the hypothesis which influence their behaviour
What is a placebo?
A substance with no pharmological effect
