🧠 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
/
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
Define practice effects
A situation where participants’ performance improves because they experience the experimental task more than once, due to familiarity or learning the task
Define fatigue effects
A situation where participants’ performance declines because they experience the experimental task more than once, e.g. due to physical tiredness or boredom with the task
What are the two ways to overcome order effects in repeated measures design?
Randomisation and counterbalancing
How does randomisation overcome order effects?
Each participant is allocated to perform in the different levels of the IV in a way that ensures they have equal chance of participating in the different levels in any order.
How does counterbalancing overcome order effects?
Each possible order of levels of the IV is performed by a different sub-group of participants.
What is ABBA design?
A way of counterbalancing where half the participants do condition A then B, and the other half do condition B then A.
Define matched pair design
An experimental design in which participants are arranged into pairs. Each pair is similar in ways that are important to the study and one member of each pair performs in a different level of the IV.
In what ways can participants be paired in matched pair design?
Age, gender, intelligence, personality
What are the ideal matched pairs?
Identical twins - they are genetically the same and live through similar experiences
What are the strengths of matched pair design?
- Participants see only one level of the IV, reducing the effect of demand characteristics
- Participant variables are less likely to distort the effect of the IV than in an independent measures design as individual differences are matched
- Different participants are used in each level of the IV so there are no order effects
What are the weaknesses of matched pair design?
- The similarity between pairs is limited by the matching process, so the right matching criteria must be chosen in advance for this to be effective
- Availability of matching pairs may be limited, making the sample size small
What are the three types of experiments?
Lab, Field, and Quasi
What is meant by operationalising the IV / DV
Breaking down the IV into different measurable levels that can be manipulated, and the DV into different measurable levels that can be observed.
Define operational definition
The clear description of a variable such that it can be accurately manipulated, measured, or quantified, and the study can be replicated. This includes the way that the IV and DV in experiments, and the co-variables in correlations, are described.
Define laboratory experiment
A research method in which there is an IV, a DV, and strict controls. It looks for causal relationship and is controlled in a setting that is not the usual environment for the participants with regard to the behaviour they are performing
What are the characteristics of lab experiments?
- An IV and DV
- Standardised procedure
- Full control of variables
- Takes place in lab / artificial situation
Define controls
Ways to keep potential confounding variables constant, for example between levels of the IV, to ensure measured differences in the DV are likely to be due to the IV, raising validity.
Define standardisation
Keeping the procedure for each participants in a study exactly the same to ensure that any differences between participants or conditions are due to the variables under investigation rather than the way they were treated
Define reliability
The extent to which a procedure, task, or measure is consistent and replicatable
Define validity
The extent to which the researcher is testing what they claim to be testing / intend to
What can be done before an experiment to identify uncontrolled variables?
A pilot study
Define pilot study
A small-scale test of the procedure of a study before the main study is conducted.
What is the aim of a pilot study?
To ensure that the procedure and materials are valid and reliable, so they can be adapted if not.
Define replication
Keeping the procedure and materials exactly the same between studies when attempting, for example, to verify results or to enable other studies to use exactly the same techniques to answer related questions.
Define placebo
A pill or procedure given to a patient who believes it to be a real treatment which doesn’t really have any active ‘ingredient’
What are the strengths of laboratory experiments?
- Highest control of extreneous variables, raising validity and reliability
- Causal relationships can be determined as only the IV should be affecting the DV
- Standardised procedures raise reliability and allow replication
- Higher internal validity
What are the weaknesses of laboratory experiments?
- The artificial situation leads to low mundane realism, making participants’ behavior unreliable.
- Low ecological validity
- Participants can respond to demand characteristics and alter their behavior
Define mundane realism
The degree to which the materials and procedures involved in an experiment are similar to events that occur in the real world
Define ecological validity
The extent to which the findings of research conducted in one situation would generalise to other situations. This is influenced by whether the situation (e.g. a laboratory) represents the real world effectively and whether the task is relevant to real life (has mundane realism)
Define generalise
To apply the findings of a study more widely
Define field experiment
An investigation looking for a causal relationship in which an independent variable is manipulated and is expected to be responsible for changes in the dependent variable. It is conducted in the normal environment for the behavior being investigated and some control of variables is possible
What are the characteristics of a field experiment?
- An IV and a DV
- Takes place in the natural environment of participants
- Standardised procedure
What are the strengths of field experiments?
- As participants are in their normal situation for the activity, they are likely to behave naturally, making the results generalisable
- Less demand characteristics as participants are unaware of being in experiment
- Higher ecological validity and mundane realism
- Higher external validity
What are the weaknesses of field experiements?
- Control of extraneous variables are less than in laboratory experiments, lowering reliability
- Researcher will be less certain that changes in the DV are caused by changes in the IV compared to a laboratory experiment.
- Participants are decieved, thus ethical issues
Define Quasi / Natural experiment
An investigation lookin for a causal relationship, where the IV is not manipulated and is rather found naturally, and there is no random assignment. It is conducted in a normal environment.
What are the strengths of Quasi experiments?
- High ecological validity
- High mundane realism
What are the weaknesses of Quasi experiments?
- Time consuming
- Deception - breaks ethical guidelines
- Can’t control extraneous variables
- Low reliability as it cannot be replicated
Define external validity
The extent to which the results of a research can be applied or generalised to another context.
What are the two types of external validity?
Ecological validity and population validity
Define population validity
Refers to how well the experimental sample represents the group
Define internal validity
The degree of confidence that the causal relationship being tested exists and is trustworthy
Why is it not possible for an experiment to have high internal and external validity?
Increased internal validity generally means that mundane realism is reduced, thus reducing external validity.
Increased external validity generally means that there is less control of extraneous variables, thus reducing internal validity
Define social desirability bias
When participants act or behave in a manner that is socially acceptable.
