Term
| Threats to Internal Validity: History |
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Definition
- Threatens when events occure between the pretest and posttest of a research study that could affect participants in such a way as to impact the dependent variable
- ex) stress, natural disasters, news events, illness
- To control history effect researcher should use a control group
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Term
| Threats to Internal Validity: Maturation |
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Definition
- Occurs when changes are seen in subjects because of the time that has elapsed since the study began and that may not be the result of any program effects
- ex) over time the participant may have become older, wiser, stronger, or more experienced
- most common when children are studied
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Term
| Threats to Internal Validity: Testing |
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Definition
- Often necessary to pretest participants before beinning a study to establish a basline level, which is a measurement taken to obtain the status or level of variable prior to initating a study.
- participants may learn how to do better on the test or be "test-wise" the next time they take the test
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Term
| Threats to Internal Validity: Instrumentation |
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Definition
- Can cause threats to internal validity when measurements are not used accurate or procedures are not standardized
- written instruments must accurately measure wheat they are supposed to measure or internal validity will be threatened.
- physical equipment must be carefully calibrated to give consistent and accurate results
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Term
| Threats to Internal Validity: Selection Bias |
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Definition
- introduces the possibility that participants in experimental and control groups may have differences before the start of the study that could account for any differences found between groups during the study, instead of such differences being due to the effects of the independent variable
- occurs when individuals are selected in nonrandom manner
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Term
| Threats to Internal Validity: Selection Maturation Effect |
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Definition
- occurs when using intact groups that vary in their maturation level
- pretesting and/or prescreening groups on maturity levels is a way to avoid this threat to internal validity
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Term
| Threats to Internal Validity: Statistical Regression |
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Definition
- occurs when participants are selected on the basis of their extremely high or low scores
- essentially, those who scored the highest may have nowhere to move but down, and those what scored the lowest have nowehere to move but up
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Term
| Threats to Internal Validity: Mortality/Attriction |
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Definition
- in longterm studies some participants may die or be in such poor state of health they cannot complete the study
- participants may move and not provide updated contact info and will be lost to the study
- participants may drop out of the study
- Oversampling and using large group sizes is one way to overcome mortality. Using incentives to stay in the study can also help reduce mortality
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Term
| Threats to Internal Validity: Hawthorn Effect |
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Definition
- Occurs when participants' attitudes toward being involved in a study affect the way they behave
- To control Hawthorn effect, researcher may try to provide the control group with some type of special treatment that is comparable to the experimental groupo but would not have a direct impact on the dependent variable
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Term
| Threats to Internal Validity: Placebo Effect |
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Definition
- Caused by participants' expectations rather than by any provided treatment
- To control placebo effect, participants are unaware if they have the real treatment or a placebo it is ablind study. If researcher does not know who is taking the real treatment or placebo it is a double blind study
- To avoid placebo effect, researchers make sure the control and experiemental groups receive the same information
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Term
| Threats to Internal Validity: Diffusion of Treatment |
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Definition
- Occurs when the treatment being applied to one groupo spills over or contaminates another group
- ex) when group A tells group B about what they are doing and causes the group B to do what group A was doing
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Term
| Threats to Internal Validity: Location |
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Definition
- Occurs when there are differences in the locations where interventions take place
- Best method to control for a location effect is to make the locations the same for all participants. Researcher should do everything possible to minimize location differences that could impact the dependent variable
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Term
| Threats to Internal Validity: Implementation |
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Definition
- Involves the individual or individuals responsible for implementing the experimental treatment and the possibility that they may inadvertently introduce inequality or bias into the study
- Can occur if there are multiple people providing the treatment program or intervention, they may not be equal in their knowledge levels, understanding of the program, personality traits, presentation skills, etc
- Can be controlled by trying to make sure that all persons responsible for implementing the program are equally trained and competent, and by following a standardized protocol for implementation
- can occur is an indicidual implementing the intervention inadvertently favors one group over another
- can be controlled if someone other than the program developer presents the program
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Term
| Threats to External Validity: Selection Treatment Interaction |
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Definition
- Concerns the ability of a researcher to generalize the results of a study beyond the groups involved in the study
- ex) overgeneralizing to groups for whom the study results might not apply (assume results of experiment are valid then results for group being studied are valid for group being studied)
- ex) a study uses a random sample of participants, results can legitimately be generalized to the group from which the random sample was selected
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Term
| Threats to External Validity: Setting Treatment Interaction |
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Definition
- Concerns the extent to which the environmental conditions or setting under which an experimental study was conducted can be duplicated in other settings
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Term
| Threats to External Validity:History Treatment Interaction |
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Definition
- Develops when the researcher tries to generalize findings to past and future situations.
- Some experiments may be time-sensitive and may not produce similar results if conducted earlier or later
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