Experimental methods/designs Flashcards
experimental method
involves the manipulating of an independent variable to measure the effect of the dependant variable
variables
any ‘thing’ that can vary or change within an investigation. typically used to determine causality
Independent variable (IV)
an aspect of the experiment that is manipulated by the researcher (or changes naturally) so the effect on the DV can be measured
Dependant variable (DV)
the variable that is measured by the researcher
extraneous variable (EV)
additional, unwanted variables that might potentially interfere with the IV or DV, and should be removed or controlled
confounding variable (CV)
a second unintended IV, which systematically changed with the IV, causing changes in the DV which affects the validity of results
demand characteristics
participants will change their natural behaviour in line with their interpretation of the aims of the study
Lab experiment
conducted under controlled conditions in which the researcher manipulates the IV, to measure the effect on the DV. often involves an artificial task or situation
Field experiment
conducted in natural conditions in which the researcher manipulates the IV, participants typically do not know they are taking part
natural experiment
where the researcher doesn’t manipulate the IV and instead examines the effect of a naturally occurring IV on the DV
quasi experiment
where the IV is an existing difference between people
strengths of a lab experiment
-extraneous variables can be controlled
-ethical due to informed consent and right to withdraw
weaknesses of a lab experiment
-situation is often artificial and cannot be generalised to everyday life
-may respond to demand characteristics
strengths of a field experiment
-natural, uninfluenced behaviour
-less likely to respond to demand characteristics
weaknesses to a field experiment
-extraneous variables cannot be controlled
-ethical issues raised such as lack of consent
strengths of a natural experiment
-naturally occurring variables are investigated, so reflective of real life
-opportunity to study situations that may otherwise be impossible to study due to practical reasons
weaknesses of a natural experiment
-participants can’t be randomly allocated
-naturally occurring events may be rare, reducing opportunities for research
strengths of a quasi experiment
-pre existing variables are investigated
-often in controlled conditions where extraneous variables are removed
weaknesses of a quasi experiment
-low control over pre existing variables
-people cannot be randomly allocated
experimental design
the way in which participants are used in experiments in relation to the different experimental conditions
independent groups
when two separate groups of participants experience two different conditions of the experiment.
repeated measures
all participants experience both conditions of the experiment
matched pairs design
where participants are paired together on a variable or variables relevant to the experiment
strengths of independent groups
-no problems caused by order effects
-less likely to guess aim of study and respond to demand characteristics
weaknesses of independent groups
-individual differences present
-requires twice as many participants (less economical)
strengths of repeated measures
-individual differences won’t affect results
-don’t need as many participants
(more economical)
weaknesses of repeated measures
-problems caused by order effects
-more likely to guess aim of study and respond to demand characteristics
strengths of matched pairs
-no order effects
-no individual differences
weaknesses of matched pairs
-expensive
-time consuming
generalisation
the application of the results from a study, to the wider target population
qualitative data
non-numerical, subjective data, expressed in words. it allows researchers to develop an insight into participants opinions, feelings and thoughts.
quantitative data
objective, numerical data that can be statistically analysed to reveal trends or patterns
reliability
a measure of consistency between participants
validity
refers to whether something is true or accurate
order effects
where learning or boredom affects the second condition
pilot study
a small-scale practice investigation carried out prior to the real investigation to identify potential problems with the design, method or analysis, so that amendments can be made
why might a researcher use a pilot study for a questionnaire
if participants where confused by certain questions, they can be re-worded more clearly
why might a researcher use a pilot study for an observational study
to see if they have missed out an important category on a behavioural checklist, or if the behavioural categories are not specific enough
