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Research Methods - Experiments (Control of Variables (Extraneous Variables…
Research Methods - Experiments
Experimental Method
- Involves the manipulation of an independent variable to measure the effect on the dependent variable. Experiments may be laboratory, field, natural or quasi
Aim
- A general statement of what the researcher intends to investigate; the purpose of the study
Hypothesis
- A clear, precise, testable statement that states the relationship between the variables to be investigated. Stated at the outset of the study
Directional Hypothesis
- States the direction of the difference or relationship
Non-Directional Hypothesis
- Does not state the direction
Variables
- Any thing that can vary or change within an investigation. Variables are generally used in experiments to determine if changes to one thing result in changes to another
Independent Variable
- Some aspect of the experimental situation that is manipulated by the researcher - or changes naturally - so that the effect on the dependent variable can be measured
Dependent Variable
- The variable that is measured by the researcher. any effect on the DV should be caused by the change in the IV
Operationalisation
- Clearly defining variables in terms of how they can be measured
Control of Variables
Extraneous Variables
- Any variable, other than the IV that may have an effect on the DV if it is not controlled. They do not vary systematically with the IV
Confounding Variables
- Any variable, other then the IV, that may have affected the DV so we cannot be sure of the true source of changes to the DV. They vary systematically with the IV
Demand Characteristics
- Any cue from the researcher or from the research situation that may be interpreted by participants as revealing the purpose of the investigation. this may lead to a participant changing their behaviour within the research situation
Investigator Effects
- Any effect of the investigator's behaviour - conscious or unconscious - on the research outcome.
Randomisation
- The use of chance in order to control the effects of bias when designing materials and deciding the order of conditions.
Standardisation
- Using exactly the same formalised procedures and instructions for all participants in a research study
Experimental Design
- The different ways in which the testing of participants can be organised in relation to the experimental conditions
Independent groups design
- Participants are allocated to different groups where each group represents one experimental condition
Repeated Measures
- All participants take part in all conditions of the experiment
Matched pairs design
- Pairs of participants are first matched on some variable(s) that may affect the DV. then one member of the pair is assigned to condition A and the other to conditon B
Random Allocation
- An attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other
Counterbalancing
- An attempt to control for the effects of order in a repeated measures design: half the participants experience the conditions in one order, and the other half in the opposite order
Laboratory Experiment
- An experiment that takes place in a controlled environment within which the researcher manipulates the IV and records the effect on the DV, whilst maintaining strict control of extraneous variables
Strengths
:
High control over extraneous variables
High internal validity
Replication is more possible
Limitations
:
May lack generalisability
Low external validity
Demand characteristics
Low mundane realism
Field Experiments
- An experiment that takes place in a natural setting within which the researcher manipulates the IV and records the effect on the DV
Strengths
:
Higher mundane realism than lab experiments
High external validity
Limitations
:
Loss of control of extraneous variables
Cause and effect may be more difficult to establish
Ethical issues - e.g. consent and privacy
Natural Experiments
- An experiment where the change in the IV is not brought about by the researcher but would have happened even if the researcher had not been there. The researcher records the effect on the DV
Strengths
:
Provides opportunities for research that may not otherwise be undertaken
High external validity
Limitations
:
The event may only occur rarely
Small scope for generalising
Participants may not be randomly allocated to experimental conditions
Quasi-experiment
- A study that is almost an experiment but lacks key ingredients. The IV has not been determined by anyone - the variables simply exist. It is strictly speaking not an experiment