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Definition
Threatens internal validity when events occur between the pretest and posttest of a research study that could affect participants in such a way to impact the dependent variable.
To mitigate this threat, a researcher could create a control group and an experimental group. These two groups are the same except the control group receives no treatment. At the end of the study, comparisons can be made between both groups. |
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Definition
Occurs when changes are seen in subjects because of the time that has elapsed since the study began.
Creating a control group would help eliminate the threat to internal validity. |
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Definition
Occurs when participants are selected in a nonrandom manner.
Rather than letting volunteers self-select a group, researchers can randomly assign them to groups which will help reduce threats to internal validity. |
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Term
| Selection maturation bias |
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Definition
Occurs when using groups that very in their maturation level.
A way to mitigate this threat to internal validity is pretesting and/or prescreening groups. |
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Definition
Occurs when participants are selected on the basis of their extremely high or low scores.
A researcher could lessen this threat to internal validity by using a random sample. |
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Definition
This refers to subjects dropping out (or moving, dying, etc.) over the course of a study.
One way to combat the morality effect is to oversample and use a large group size. |
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Definition
When participants' attitudes toward being involved in a study affect the way they behave.
One way to avoid the Hawthorne effect is to not allow participants to know they're taking part in a study. |
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Definition
Caused by participants' expectations rather than by any provided treatment.
One way to mitigate this threat is to give out as little information as possible to reduce any expectations. |
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Definition
| Occurs when the treatment being applied to one group spills over or contaminates another group. |
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Definition
Occurs when there are differences in the locations where interventions take place.
The best way to control this is to make the location the same for all participants of the study. |
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Definition
Individuals responsible for implementing the experimental treatment and the possibility that they may inadvertently introduce inequality or bias into the study.
To combat this threat, get somebody to present who is neutral and unbiased. |
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Term
| Selection treatment interaction |
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Definition
| This is a threat to external validity that concerns the ability of the researcher to generalize the results of a study beyond the groups involved in the study. |
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Term
| Setting treatment interaction |
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Definition
| The extent to which the environmental conditions under which an experimental study was conducted can be duplicated in other settings. |
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Term
| History treatment Interaction |
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Definition
| The threat to external validity that develops when the researcher tries to generalize findings to past and future situations. |
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