🧠 psychology - experiments (2) Flashcards
Define experiment
An investigation that allows researchers to look for a cause-and-effect relationship
Define Independent Variable
The factor under investigation in an experiment that is manipulated to create two or more conditions (levels) and is expected to be responsible for changes in the dependent variable.
IV
Define Dependent Variable
The factor in an experiment that is measured and is expected to change under the influence of the independent variable
DV
How should a researcher be certain that the difference in the DV in multiple conditions is caused by the IV?
The researcher has to eliminate all uncontrolled variables that might affect the DV
Define uncontrolled variable
A variable that either acts randomly, affecting the DV in all levels of the IV, or systematically (on one level of the IV), thus obscuring the effect of the IV, making the results difficult to interpret.
What are the types of uncontrolled variables?
Extraneous variable and confounding variable
Define extraneous variable
A variable that is not being investigated that can potentially affect the dependent variable of the research study.
Define confounding variable
An extraneous variable that not only affects the dependent variable but is related to the independent variable
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An uncontrolled variable that acts systematically on one level of the IV so could hide or exaggerate differences between levels of the IV
What are the three types of confounding variables?
- Situational variable
- Experimenter variable
- Participant variable
Define situtational variable
A confounding variable caused by environmetnal factors that unintentionally affect the results of a study
Define experimenter variable
A confounding variable caused by the researcher unintentionally influencing how the participant should behave
Define participant variable
A confounding variable caused by difference of characteristics of participants’ backgrounds that could affect a study’s results even if it isn’t being investigated.
Define experimental condition
One or more of the situations in an experiment that represent different levels of the IV and are compared (or to a control condition)
Define control condition
A level of the IV in an experiment from which the IV itself is absent. It is compared to one or more experimental conditions.
How can extreneous variables be reduced?
- Standardised scripts
- Constant environmental factors
- Single blind study
- Double blind study
- Matched-pair design
Define experimental design
The way in which participants are allocated to levels of the IV
What are the three experimental designs?
- Independent measures design
- Repeated measures design
- Matched pairs design
Define independent measures design
An experimental design in which a different group of participants is used for each level of the IV. Each group is randomly recruited from a larger group.
Why is it called independent measures design?
Because the data for each level of the IV is ‘independent’ as it isn’t related to any other data, due to coming from different participants
Define random allocation
A way to reduce the effect of confounding variables such as individual differences. Participants are randomly selected to be put in each level of the IV so that each person has an equal chance of being in any condition.
Define demand characteristics
Features of the experimental situation which give away its aims. They can cause participants to try to change their behavior to mathc their beliefs about what is supposed to happen, reducing the study’s validity.
What are the strengths of Independent measures?
- Different participants are used at each level of the IV so there are no order effects
- Participants only see one level of the IV, reducing the effect of demand characteristics
- Random allocation to levels of the IV can reduce the efffects of individual difference
What are the weaknesses of Independent measures?
- Participant variables can distort results if there are important individual differences between participants in different levels of the IV
- More participants are needed than in a repeated measures design so the study may be less ethical if participants are harmed and less effective if there is a small sample as participants are hard to find
Define order effects
The consequences of participating in a study more than once, causing changes in performance between conditions that are not due to the IV, so can obscure the effect on the DV
Define repeated measures design
An experimental design in which each participant performs in every level of the IV. One group repeats the test in multiple conditions.
What are the strengths of repeated measures?
- Participant variables are unlikely to distort the effect of the IV, as each participant does all levels
- Counterbalancing reduces order effects
- Uses fewer participants that independent variables or matched pairs so is good when participants are hard to find or are at risk
What are the weaknesses of repeated measures?
- Order effects could distort the results
- As participants see the experimental task more than once, they have greater exposure to demand characteristics
What are the two types of order effects?
Practice effects and fatigue effects