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Common Threats to Internal ValiditySTART: Athlone Flatline Half Marathon 2014 A study's internal validity has to do with the ability of its design to support a causal conclusion. Unsurprisingly, experimental research tends to have the highest internal validity, followed by quasi-experimental research, and then correlational research, with case studies at the bottom of the list. Nonetheless, there are several potential threats to internal validity that are especially relevant to nonexperimental designs. These include the following eight threats, which may be remembered by using the acronym "MRS. SMITH": MaturationPhysiological processes occurring within the participants that could account for any changes in their behaviour. Subjects may change between test sessions of the experiment such that any changes in scores between testing sessions may simply be due to the passage of time rather than any treatment effects. Examples:
Regression to the MeanThe tendency that participants who receive extreme scores when tested, tend to have less extreme scores on subsequent retesting even in the absence of any treatment effects.
Selection of SubjectsAny bias in selecting and assigning participants to groups that results in systematic differences between the participants in each group.
Selection by Maturation InteractionThe treatment and no-treatment groups, although similar at one point, would have grown apart (developed differently) even if no treatment had been administered.
MortalityDifferential dropping out of some subjects from the comparison groups before the experiment is finished, resulting in differences between the groups that may be unrelated to the treatment effects.
InstrumentationChanges in the measurement procedures may result in differences between the comparison groups that are confused with the treatment effects. For example:
TestingWhen participants are repeatedly tested, changes in test scores may be more due to practice or knowledge about the test procedure gained from earlier experiences rather than any treatment effects
HistoryExtraneous events occurring during the course of the experiment that may affect the participants’ responses on the dependent measure.
Activity Read through this "We're only human" news story and try to answer the following questions: 1. Clearly describe one correlational result reported in the news study. Your description should include the variables involved as well as the direction of the correlation. (6 marks) 2. Draw and clearly label a scatterplot that illustrates this correlation using 10 data points. You may wish to use the Interpreting Correlations interactive visualization to guide your drawing. (8 marks) 3. Did the researcher(s) consider whether a third variable might have influenced this correlation? If so, which variable did they measure? (2 marks) 4. How do the researchers interpret this correlation? Do they explain the correlation in a particular causal direction? Can you suggest an alternative interpretation of this correlation? (6 marks) 5. Consider how you might be able to address the same question using a different non-experimental research design. Your proposed study should use the same variables but should operationalize them differently. Briefly outline your proposed study. (8 marks)
Share your favourite example on the micro-blog discussion forum (found at the bottom of the Home Page) or on Twitter (using the hashtag #OERuPSYC2111). | What are the threats of internal validity?What are threats to internal validity? There are eight threats to internal validity: history, maturation, instrumentation, testing, selection bias, regression to the mean, social interaction and attrition.
What are the 4 threats to internal validity?History, maturation, selection, mortality and interaction of selection and the experimental variable are all threats to the internal validity of this design.
What are the three most common threats to internal validity?Threats to Internal Validity. Attrition: Attrition is bad for your research because it leads to a bias. ... . Confounding variables: When your research has an extra variable related to the treatment you applied to your sample group that affects your results, then that leads to confusion. ... . Diffusion: This is a tricky one.. What are the 4 threats to external validity?What are threats to external validity? There are seven threats to external validity: selection bias, history, experimenter effect, Hawthorne effect, testing effect, aptitude-treatment and situation effect.
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