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Field, Lab, Naturalistic and Quasi Experiments

The differences between these types of experiment and how they relate to validity and reliability.
by

Ian Harris

on 6 July 2012

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Transcript of Field, Lab, Naturalistic and Quasi Experiments

The four types of Experiment can be thought of as a product of two questions Firstly, ask yourself whether the experimenter is manipulating the independent variable or if (perhaps for ethical or practical reasons) they are working with naturally occuring variation in the IV If the IV is being manipulated, e.g.: Being given the drug or a placebo in a clinical trial Articulatory suppression activities in recall experiments Whether or not the participants were exposed to misleading post event information in leading question type EWT experiments Alternatively, let nature take its course and wait for the IV to vary naturally Testing deprivation-delinquency hypotheses like Bowlby. You have to wait for the deprivation to occur you must not go around trying to create it. Investigating birth order effects on social and emotional development. Exploring the impact of traumatic experiences on reliability of eye witness testimony, e.g. you want to know whether people whose loved ones have been hurt/killed are more or less reliable about the circumstances than someone who was relatively unaffected. The other distinguishing issue for experimental types is the amount of control we exercise over any extraneous variables With relatively low levels of control being exercised over the extraneous variables Then there's the batton down the hatches approach Think about Bartlett's war of the ghosts study being conducted in social settings so that he could claim to have examined memory as it is used in the real world The way that Loftus and Palmer style experiments often expose the participants to stimulus material in 'real life' settings before asking any questions. Bystander effect experiments in social psychology, e.g. how long it takes for people to start to leave buildings when the fire alarm sounds. It turns out that the more people there are in a space the longer it takes for them to begin to respond to fire alarms. Harlow's monkeys were carefully matched for age and earliest experiences (e.g. how long before they were permanently removed from their mothers). This gives us more confidence in attributing any changes in their behaviour to the manipulation of the IV. Then of course there's the obvious Milgram. Clearly all the relevant extraneous variables like proximity, prestige of the setting the script of the authority figure, etc. are carefully controlled to make the findings as reliable as possible. Lab Field Naturalistic Quasi Tend to be easier to replicate and have the highest reliability. We usually have most confidence in the conclusions drawn on this type of evidence about the relationship between the IV and the DV as potentially confounding EVs have been controlled Less reliable than lab but considered to have greater ecological validity. Well designed field experiments are still able to provide convincing evidence of the relationship between IV and DV but this is often more difficult to replicate so less reliable. These need more replication (peer review) to be convincing. This is because there is less confidence in variations in the results being attributed to changes in the IV. Also, since the experimentor has to work with the changes in the IV that occur naturally there can be difficulties with how representative the data collected is relative to the target population. Hardest methods to replicate reliably as there is so much changing that isn't under the direct control of the experimentor. On the plus side however, because the experimentor isn't really messing around with anything the findings are often thought to support conclusions with the greatest real world/emvironmental validity. Fie Lab at ur istic Qua si ld N al Independent Variable is manipulated by the experimentor Variations in the Independent Variable occur naturally and the experimentor works with these Extraneous Variables are subject to high levels of control Extraneous Variables are less controlled and may even be allowed to vary naturally Independent Variable is manipulated by the experimentor Variations in the Independent Variable occur naturally and the experimentor works with these Extraneous Variables are subject to high levels of control Extraneous Variables are less controlled and may even be allowed to vary naturally Laboratory or Field Experiments Naturalistic or Quasi Experiments Field and Quasi Experiments Laboratory or Naturalistic Experiments Quasi Which type of Experiment goes in which box? Lab Naturalistic Field Give each type of experiment a rating out of 4 for reliability and validity
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