Experiments Flashcards
Experiments
- This is a research method that can establish a causal (cause-and-effect) relationship between variables
- If psychologists change one feature (variable) of a situation this causes a behavioural change
Independent Variable
- Is the variable being manipulated by the experimenter
Dependent Variable
- Is the variable being measured by the experimenter
Laboratory Experiment
- This is conducted in a well-controlled environment where accurate measurements are possible
- As this uses a standardised procedure
Laboratory Experiment Evaluation
+ Easier to replicate: a standardised procedure is used
+ Precise control of extraneous and IV’s: cause and effect relationship can be established
- Artificial setting produces unnatural behaviour: low ecological validity as it cannot be generalised to a real life setting
- Demand characteristics or experimenter effects: bias the results and become confounding variable
Field Experiment
- These are done in the real life environment of participants in a real life setting
- But the experimenter still manipulates the independent variable
Field Experiment Evaluation
+ High ecological validity: behaviour is likely to reflect real life due to natural setting this creates
+ Less demand characteristics: participants may not know they are being studied e.g. if the study is covert
- Less control over extraneous variables that might bias results: makes it difficult for another researcher to replicate the study in the same way
Quasi Experiment
- Natural experiment in real life where the independent variable is occurring naturally
- E.g. investigating adopted and fostered children
Quasi Evaluation
+ Behaviour reflects real life: due to natural setting there is high ecological validity
+ Less likelihood of demand characteristics: participants may be unaware they are being studied so act naturally
+ Useful for situations where it would be unethical to manipulate the independent variable e.g. researching stress
- More expensive/time consuming
- Less control over extraneous variable that may bias results: makes it difficult for another researcher to replicate the study in the same way
Demand Characteristics
- Are when participants are led to think they know the aims of the research due to clues so they act accordingly
Order Effects
- Changes in participants’ performance due to repeating similar test
- E.g. practice effects lead to improvement due to repetition/familiarity of task
- E.g. fatigue effects decrease performance due to boredom or tiredness from repetition of task
Independent Measures
- Participants only take part in one condition of the experiment, as there will be two groups
Independent Measures Evaluation
+ Each participant only experiences one condition which reduces demand characteristics
+ If participants drop out new ones can be found
- Twice as many participants are required as there are two groups
- Doesn’t control participant variables; researcher may end up with participants in one group who are naturally ‘better’ at the DV than the other group
Repeated Measures
- Participants take part in both conditions of the experiment, as there is only one group
Repeated Measure Evaluation
+ Controls participant variables: participants in condition A are precisely the same as in condition B
+ Only a small number of participants needs to be recruited
- Situational variables occur: doing one variable first may affect performance in the other
- Demand characteristics as they can predict the aim from both conditions
Matched Pairs
- Participants are matched in each condition for characteristics that may have an effect on their performance
Matched Pairs Evaluation
+ Participant variables are controlled as they are matched across the conditions
+ There are no problems with order effects
- If one participant drops out a new match must be found or risk losing two sets of data
- Requires hard work to match participants e.g. on IQ which requires testing
Counterbalancing
- Overcomes the problem of order effects
- Half the participants do condition A first followed by B and the other half do condition B followed by A
Operationalising Variables
- How well you define and measure a specific variable as it’s used in the study
- E.g. instead of “young participants will have significantly greater memories than older participants,” you would say, “participants aged between 16-30 will recall significantly more nouns from a list of twenty than participants aged between 55-70”
- This provides a clearer and objective definition of even complex variables, making it easier for researchers to replicate a study and check for reliability
Extraneous Variables
- Variable which are not the IV but could affect the DV, these should be controlled
Situational Variables
- Aspects of the environment that may affect the participant’s behaviour
- E.g. noise, temperature or order effects
- This can be controlled by using a standardised procedure to ensure that the conditions are all the same for all participants
Participant Variables
- Ways that participants vary from each other
- E.g. intelligence, concentration or mood
- This is controlled by using random allocation to conditions of independent variable or by counterbalancing
Experimenter Variables
- Unintentional ways that the experimenter gives clues to participants about the expected behaviours of the study
- This is controlled by using single blind or double blind methods
Confounding Variables
- Variables that have affected the DV apart from the IV
- An extraneous variable that hasn’t been controlled
Test-Retest-Reliability
- Ensures that the experiment gives the same results when repeated at another time or place
Inter-Rater-Reliability
- Ensures that the experiment gives the same result when carried out by a different investigator
