Term
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Definition
Definition:
When events occur between the pretest and posttest of a research study that could affect participants in such a way as to impact the dependent variable.
Address Concern By:
Use a control group not exposed to the treatment and compare it to the experimental group. |
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Term
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Definition
Definition:
Changes in a subject that occur since the start of the study that may not be the results of the program effects. The participant may have become older, wiser, stronger or more experienced.
Address Concern By:
Utlize a control group to compare with the experimental group to determine if the experiment was the result of the change or if maturation was. |
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Term
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Definition
Definition:
When a participant learns how to better take a test on a posttest having taken the prettest. This can be cognative and biological, in that a participant's body can react differently on a post test since they have taken the prettest and know what to expect.
Addrss Concern By:
Use a control group that does not participate in a prettest in order to minimize threat to internal validity. |
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Term
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Definition
Definition:
When measurements are not accurate or procedures are not standardized, a threat to internal validity can occur. Writen items must ask correct questions.
Address Concern By:
Well designed instruments and proper training can reduce threats to internal validity. |
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Term
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Definition
Definition:
Selection bias occurs when subjects are selected through non-random sampling. Participants may have differences prior to the study which could impact intenral validity.
Address Concern By:
Recruiting volunteers then randomly assigning them to the groups. Match participants on selected criteria then randomly assign them. Pretest groups on measures of the dependent variable to make sure there are not pretreatment differences between groups. |
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Term
| Selection Maturation Effect |
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Definition
Definition:
The combination of Selection Bias and Maturation threat. This is using intact groups that vary in their muturation levels.
Address Concern By:
Pretesting or prescreening groups on maturity levels. |
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Term
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Definition
Definition:
When subjects are selected based on high or low scores. Those that score the highest have no where else but to move down in score, and those that score the lowest have no where else to move but up in the score.
Address By:
Random sampling reduces this threat as the study would then not focus on those with the highest and lowest score results. |
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Term
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Definition
Definition:
Loss of subjects due to death or relocation without having contact information. It negative impacts validity by reducing the ability to compare groups when one group falls below stastical analysis. Also reduces generalizablility for larger population.
Address Concern By:
Larger sampling population to reduce chances of being left with a small sample size as well as incentives are two ways to reduce this threat. Measure the impact of mortality on the research by obtaining strong demographic information on participants and then compare group at start with at end to determine if makeup of group has changed. |
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Term
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Definition
Definition:
When participants attidues about being part of the study impact their behaviors.
Address Concern By:
Provide control group with a similar special treatment. Keep participants from knowing they are taking part in a study or being observed, though this is not usually allowed given the need for full disclosure. |
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Term
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Definition
Definition:
Caused when participants expect a change to occur, therefore the change occurs as oppose to occuring from the treatment.
Address Concern By:
Use of placebo group, blind or double blind study. Can also provide the same information to both experiement and control group or provide minimal information to both groups. |
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Term
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Definition
Definition:
When treatment being provided to one group spills over or contaminates another group.
Address Concern By:
Explain nature of the study to participants and stress confidentiality until end of the study. |
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Term
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Definition
Definition:
When location impacts the outcome of the study.
Address Concern By:
Idally having the location the same for all participants. Miminize location differences as much as possible. |
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Term
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Definition
When the person(s) administering the experiment treatment introduce bias or inequality in the study. This can occur when multiple individuals are adminstering the experiment treatment but don't have the same level of knowledge or understanding of the program. If those implementing the experiment favor one group over the other.
Address Concern By:
Provide equal training to all those administering the experiment. Another way is to have all the individuals administering the experiment talk to all groups. Have a neutral person explain the experiment to the groups or have a neutral observer watch the explaination to make sure they are done the same way. |
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Term
| Selection Treatment Interaction |
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Definition
Concern with generalizability of findings.
Address Concner By:
Using intack groups and not generalizing the findings beyond the group. Use random sampling and generalize finding to study population. |
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Term
| Setting Treatment Interactions |
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Definition
Whether the environmental conditions or setting in one study can be replicated in another study.
Address Concern By:
Random sampling from similar participants and settings.
Address Concern By: |
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Term
| History Treatment Interaction |
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Definition
When researchers try to generalize findings to past or future situations. Some experiences are time sensitive and may not produce the same results in an earlier or later time.
Address Concern By:
Considering variables related to time which could impact results of the study. |
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