Experiments
Keywords
Independent variable: variable being manipulated
Dependent variable: variable being measured
Operationalise: specify in enough detail to make replication possible
Research aim: states what the researcher intends to find out. It is phrased as a statement starting with ‘To investigate’
Research question: rephrases the aim as a question
Hypothesis: a precise and testable statement that makes a prediction
One tailed hypothesis: statement that predicts the direction of results
Two tailed hypothesis: statement that does not predict the direction of results
Null hypothesis: statement that predicts no pattern or trend in results
Alternative hypothesis: statement that predicts a pattern or trend in results
Experimental method: choice a researcher makes as to how they chose to conduct their experiment
Types of experiments
Laboratory: IV is manipulated in a highly controlled environment specially designed for the experiment
Strengths: high control over extraneous variables, accurate measure of data, easy to replicate so has high internal vailidiry and high interval reliability
Weaknesses: Participants are aware they are being studied so may show demand characteristics, decreasing internal validity and has low ecological validity/is less generalisable
Field: IV is manipulated but in an uncontrolled environment
Strengths: High ecological validity and participants are often unaware they’re being studied so show less demand characteristics, increasing internal validity
Weaknesses: hard to control extraneous variables so has low internal validity, and is less replicable so has low internal reliability
Quasi: IV is not manipulated, it is naturally occurring
Strengths: High ecological validity , is more generalisable and participants are less likely to show demand characteristics, increasing internal validity
Weaknesses: less scientific due to no manipulation, difficult to establish control over extraneous variables, decreasing internal validity , and it may be difficult to find participants
Confounding variable: any variable other than the IV that has affected the DV
Extraneous variables: any variable other than the IV that may have affected the DV
Extraneous variables
Participant variables: characteristics of the participant that may affect the results. (Can be controlled for using a larger sample, repeated or matched participants design, or random allocation to conditions)
Situational variables: a feature of the situation that may affect the results
Environmental variables: feature of the research environment that may affect the results. (Can be controlled by standardisation)
Order effects: caused by repeated measures designs when the participant may do better/worse in the second condition due to practice/boredem. (Can be controlled by counterbalancing)
Demand characteristics: participants guess the aim of the study and change their behaviour, possibly affecting the results. (Can be controlled by single blind trials or deception)
Researcher bias: subtle or deliberate cues from a researcher to encourage certain behaviours in participants, which may affect the results. (Can be controlled using a double blind trial or inter-rater reliability)
Researcher effects: anything the researcher does that has affected results (confounding variables)
Control group: group that does not receive treatment/manipulation from the researcher as a benchmark to measure the other test subjects by comparison
Experimental design: decision about whether to have one group of participants do both condition or have more than one group of participants do only one condition
Experimental designs
Independent measures design: using different participants for each independent variable
Strengths: no order effects and less demand characteristics, increasing internal validity
Weaknesses: more participants needed and participant variables differ, decreasing internal validity
Repeated measures design: using the same participants for each independent variable
Strengths: less participants needed and participant variables remain constant, increasing internal validity
Weaknesses: order effects and more demand characteristics, decreasing internal validity
Matched participants design: participants are matched on a relevant participant variables. One member of each pair is allocated to each independent variable
Strengths: no order effects, less demand characteristics and participant variables remain constant, increasing internal validity
Weaknesses: more participants needed and it all participant variables can be controlled for