research methods - types of experiments

• define what experimental methods are


  - refers to the method used to carry out the experiment
• describe what experimental methods aim to find

  - experimental methods are attempting to find a cause and effect relationship between an independent variable and dependent variable, and to measure the extent of this effect
• define what a laboratory experiment is

  -controlledconditions, independent variable is manipulated by researcher to measure effect on dependent variable- conditions are heavily controlled to minimise effect of any extraneous variables, to prevent them from becoming a confounding variable which may adversely affect the DV
• describe the advantages of a laboratory experiment

  - high degree ofcontrolover EV, EVs less likely to become confounding variables which negatively affect DV =high internal validityso conclusions about cause and effect can be drawn between IV and DV- more easily replicated, greater control means less chance that new EVs are introduced = findings can be confirmed, supporting theirvalidity

  
• describe the disadvantages of a laboratory experiment

  -lacks external validity:ppts aware they're part of the investigation (due to the contrived nature of the situation which may feel unlike real-life), study can lackecological validity= findings can't be generalised to settings beyond the laboratory as the tasks often lackmundane realismand wouldn't be every day life occurrences- demand characteristics, these are cues in the experimental situation that invite a particular response from ppts = the findings may be explained by these cues rather than the effect of the IV (lower internal validity)

  
• give an example of a study that is a laboratory experiment

  - Milgram

  
• define what a field experiment is

  -natural conditions, researches manipulates IV to measure effect on DV, not in a lab,everyday life

  
• describe the advantages of a field experiment

  - more natural environment so ppts more comfortable and behaviour more authentic =high ecological validity, results more likely to be generalised- ppts unaware of being studied, they're more likely to behave as they normally do = highexternal validity, findings can be generalised- higher mundane realism

  
• describe the disadvantages of a field experiment

  -less controlover EV = these can become confounding variables, can distort findings, firm cause and effect relationship cannot be drawn since other factors could've had impact on DV, other than IV -lower internal validity-ethical issues= ppts unaware,no informed consent, breach of privacy rights, need cost-benefit analysis before proceeding with any study to ensure the perceived outcomes from the research will outweigh any personal costs to those involved-low replication

  
• give an example of a study that is a field experiment

  - Bickman
• define what a natural experiment is

  - researcherdoesn't manipulate IV,examineseffectof existing IVon DV- IV is naturally occurring- DV may be naturally occurring or may be devised by the experimenter and measured in the field or a lab- behaviour of people affected is either compared to their own behaviour beforehand, when possible, or with a control group who have not encountered the IV- IV is natural, not necessarily the context (place)
• describe the advantages of a natural experiment

  - naturally occurring IV. real-world issues =higher external validity,so findings are more relevant to real experiences-high in ecological validityas its less artificial- may be only viable/ethical option, may be unethical to manipulate the IV = natural experiment may be only way causal research can be done for such topics- uniqueinsightsinto real-life situations, investigating naturally occurring IV allows research to be conducted into areas that couldn't be generated for ethical reasons or because of logistical and practical constraints- more ethical (aggression)
• describe the disadvantages of a natural experiment

  - interesting natural event is rare = maylimit the scopeforgeneralising findingsto other similar situations- no control over environment andsubsequent EV= difficult for research to accurately assesseffects of IV on DV, may be aconfounding variablethat has affected results so a cause and effect relationship must be drawn with extreme caution, if at all- ppts not randomly allocated, experimenter has no control over which ppts are placed in which condition as IV is pre-existing,lacks cause and effect=low internal validity, may result in confounding variables(e.g. Romanian orphans adopted early may also be the friendlier ones)
• give an example of a study that is a natural experiment

  - Rutter (Romanian orphan, raised in awful conditions)
• define what a quasi experiment (cross-sectional study) is

  - naturally occurring IV, but one thatalready exists- IV is a difference between people (e.g. age, gender), study effect of IV on DV- don't have to be in natural settings
• describe the advantages of a quasi experiment

  - high control = replication is possible- comparisons can be made between people- depends on if it is a lab/field/natural
• describe the disadvantages of a quasi experiment

  - methodological issues = no control over EV, often lacks ecological validity, findings can't be generalised- ppts not randomly allocated = confounding variables
• give an example of a study that is a quasi experiment

  - Sperry (brain separated)