Experiments (Method + Design) Flashcards
what is the experimental method?
an experiment sets out to test a research aim and hypothesis.
What is a true experiment?
a study of difference and is nomothetic. differs from non-experimental methods, involves deliberate manipulation of one variable while trying to keep all other variables constant.
What is the IV?
Independent Variable- research manipulates
What is the DV?
Dependent Variable- variable that is measured
Characteristics of a true experiment
- Researchers are looking for a different between conditions
- Researcher look to manipulate the operationalised IV
- Control (Extraneous Variables) and measure/record a change in the operationalised DV
- Researchers will randomly allocate participants to each condition
Types of experiments
-Laboratory Experiment
-Field Experiment
-Quasi Experiment
-Natural Experiment
Experimental Designs include:
repeated measures, independent group, matched pairs
What is the independent group design?
Different participants are placed in each condition. it is used to ensure that results are not influenced by order effects, to reduce the chance of demand characteristics and when repeated measured designs cannot be used
Strengths of Independent group design:
-researchers only need to produce one set of stimulus materials
-order effects are reduced bc participants only experience one condition, increases validity
-reduces chance of demand characteristics
Limitations of Independent group design:
-individual differences may confound the results
-more participants are required than in other designs, makes design expensive to use large sample size
What happens in Repeated Measures Design?
Same participants are used in both conditions.
Used to reduce the influence of individual differences and where participants are difficult to sample
Strengths of repeated measures design:
-individual results do not affect the results or any subsequent conclusions
-design is efficient; only one set of participant expenses
Limitations of repeated measures design:
-participants experience both conditions so demand characteristics might confound the results
-at least 2 sets of stimulus materials are required
-increased chance of demand characteristics
What happens in Matched pairs design?
different participants are used in each condition but they are matched on key variables to form pairs
Strengths of matched pairs:
-researchers only need to produce one set of stimulus materials, reduces chances of confounding variables associated with the materials
-order effects are reduced bc participants only experience one condition- validity
Limitations of matched pairs:
-matching pairs is difficult, time consuming and may be inaccurate/incomplete/invalid
-attrition might be an issue
What is meant by operationalised?
when researchers operationalise variables, they express them in a form that can be measured accurately.
What are extraneous variables?
EV are variables that might affect the results that haven’t been controlled.
What are cofounding variables?
a variable that influences both the dependent variable and independent variable
What is a Laboratory experiment?
Take place in lab
Independent variable is directly manipulated by researcher and effect on the dependent variable is measured
Extraneous variables controlled as much as possible
Strengths of lab experiment:
-cause and effect can be inferred as isolation of effects of independent variable on dependent variable
- strict controls and well documented procedure: can replicate and check reliability of findings
-specialist equipment can deepen understand of behaviour
Limitations of lab experiments:
-artificial context means participants do not demonstrate natural behaviour: reduces ecological validity
- demand characteristics are likely: may look to researcher for clues and adjust behaviour accordingly
- impossible to use in situations where would be inappropriate to manipulate IV for practical or ethical reasons
What is a field experiment?
Same as lab experiment in the sense of IVs and DVs and EVs but lab experiment is swapped for real-life setting
Strengths of field experiments:
-external (ecological) validity is higher than lab: can generalise findings to other settings
-demand characteristics are decreased compared to lab experiment: if participants are unaware they are taking part, they act naturally
Limitations of field experiment:
- control of extraneous variables reduces in real world: reduce validity of results if lots
-if unaware they are taking part may get distressed: difficult to gain fully formed consent to debrief them
- researcher has no control over participants who take part, samples may be biased: population validity if reduced
- opportunity sampling
What is a quasi experiment?
Experiment with high degree of control of extraneous variables, researcher manipulated independent variable to find out it’s effect on dependent one.
Researcher is unable to freely manipulate the independent variable or randomly allocate participants to the two conditions
Strengths and limitations of quasi experiment:
Similar strengths and weaknesses to lab experiment
BUT
no random allocation of participants- so participant variables more likely to confound the results compared to lab experiment
What is a natural experiment?
No manipulation or control of any of the variables- naturally occurring
Strengths of natural experiment:
-allow researchers to investigate topics that would be impractical and/or unethical to investigate using other methods
-ecological validity extremely high compared to lab. Able to study completely ‘real’ problems
-demand characteristics greatly reduced compared to lab experiment
Limitations of natural experiments:
-no random allocation of participants: participant variable more likely to confound results
-researcher has no control over environment; extraneous variables reduced validity of results
-ethical guidelines are breached if unaware taking part in research (informed consent, confidentiality, right to withdraw)
-natural events to study are rare, often impossible to replicate research to test findings for reliability
What is counter balancing (repeated measures design)
Used to over come order effects
- order of conditions is mixed up so half experience experimental condition then control and half the other way around
-although doesn’t eliminate order effects, mean any order effects are now equal across both conditions, so negative effect is reduced
What is standardisation?
Process by which a researcher will establish a uniform procedure
-often achieved by developing written instructions to instruct participants what is expected of them