What is the difference between internal and external validity? List the threats
ID: 1201083 • Letter: W
Question
What is the difference between internal and external validity? List the threats to internal validity, and how we combat these. Is a study automatically non-usable if the results are not externally valid? Why or why not? What is the difference between internal and external validity? List the threats to internal validity, and how we combat these. Is a study automatically non-usable if the results are not externally valid? Why or why not? What is the difference between internal and external validity? List the threats to internal validity, and how we combat these. Is a study automatically non-usable if the results are not externally valid? Why or why not?Explanation / Answer
Internal validity refers to how well an experiment is done, especially whether it avoids confounding (more than one possible independent variable [cause] acting at the same time). The less chance for confounding in a study, the higher its internal validity is.
Therefore, internal validity refers to how well a piece of research allows you to choose among alternate explanations of something. A research study with high internal validity lets you choose one explanation over another with a lot of confidence, because it avoids (many possible) confounds.
External validity refers to the degree to which the results of an empirical investigation can be generalized to and across individuals, settings, and times. External validity can be divided into • Population validity • Ecological validity
THUS
A distinction can be made between internal and external validity. These types of validity are relevant to evaluating the validity of a research study / procedure.
Internal validity refers to whether the effects observed in a study are due to the manipulation of the independent variable and not some other factor. In-other-words there is a causal relationship between the independent and dependent variable.
Internal validity can be improved by controlling extraneous variables, using standardized instructions, counter balancing, and eliminating demand characteristics and investigator effects.
External validity refers to the extent to which the results of a study can be generalized to other settings (ecological validity), other people (population validity) and over time (historical validity).
External validity can be improved by setting experiments in a more natural setting and using random sampling to select participants.
Threats to internal validity
History is a threat for the one group design but not for the two group design.Events outside of the study/experiment or between repeated measures of the dependent variable may affect participants' responses to experimental procedures. Often, these are large scale events (natural disaster, political change, etc.) that affect participants' attitudes and behaviors such that it becomes impossible to determine whether any change on the dependent measures is due to the independent variable, or the historical event.
Maturation: Subjects change during the course of the experiment or even between measurements. For example, young children might mature and their ability to concentrate may change as they grow up. Both permanent changes, such as physical growth and temporary ones like fatigue, provide "natural" alternative explanations; thus, they may change the way a subject would react to the independent variable. So upon completion of the study, the researcher may not be able to determine if the cause of the discrepancy is due to time or the independent variable.
Statistical regression: An effect that is the result of a tendency for subjects selected on the bases of extreme scores to regress towards the mean on subsequent tests. When measurement of the dependent variable is not perfectly reliable, there is a tendency for extreme scores to regress or move toward the mean. The amount of statistical regression is inversely related to the reliability of the test.
Selection:If subjects were selected by random sampling and random assignment, all had equal chance of being in treatment or comparison groups, and the groups are equivalent.
Experimental mortality is also known as attrition, withdrawals, or dropouts and is problematic when there is a differential loss of subjects from comparison groups subsequent to randomization, resulting in unequal groups at the study's end. One example is a study designed to compare the effects of an intranasal corticosteroid spray with placebo in alleviating symptoms of allergic rhinitis. If subjects with the most severe symptoms preferentially dropped out of the active treatment group, the treatment may appear more effective than it really is.
YES,the study is not usable if results are not valid externally as it cant be used to produce generalized statements and laws.
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