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:

Include a control group to the research design so that external forces can be measured for.

Definition:

effect 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 an program effects. Such as studying kids strength as they grow up.

Address concerns by:

Incorporate a control group into your research design to eliminate threats to internal validaty.

Definition:

Is the effect that establishing difference in results based on a pre-test (baseline) with a post-test.  This happens because the participant knows what to expect after taking the pre-test, and therefore can better prepare themselves for the post-test.

Address concerns by:

Including a control group into the research design.  This control group should not be subjected to a pre-test, which will gage the testing affect of the experimental group.

Instrumentation

Definition:

The threat to internal validity when measurements/procedures are not accruately carried out.

Address concern by:

Well trained research administrators as well as well thought out questions/research projects can decrease this threat to internal validity.

Defintion:

When a research group is not selecte at random. 

Address Concerns by:

Trying to include random selection in each research group.  If this is not possible, then trying to seperate simular participants into seperate groups can help reduce this threat to internal validity.  Also never allow participants to select their own group.

Defintion:

This happens when using pre-established research groups that vary in their maturaiton level. 

Address concerns by:

Pretesting and/or prescreening groups on maturity levels.

Definition:

The effect when gropus of high or low on original test move to the statistical average upon next testing.

Address conerns by:

A research design with a random sample would help rather than focusing solely on the two extremes.

Definition:

When particpant's attitudes towards being involved in a study affect the way they behave.

Address concern by:

Try to give each group, control and experimental, the same amount of attention.  Also, though unethical, one could not inform participants that they are a part of a research experiment.

Defintion:

Is cause by particpant's expectations rather than by any provided treatment.  This is often done in medical research.

Address concern by:

Have the research design incorporate a blind or double blind approach.  That balances the potential effect between both the control group and the experimental group.

Definition:

Occurs when the treatment being applied to one group (experimental group) spills over to other participants (control group).

Address concern by:

It is best to try and have the control and experimental groups completely seperate from each other.  This can best be done by by changing locations in order to make sure both groups do not have contact with one another.

Defintion:

occurs when there are differences between two geographical places in which the research is being conducted. If one group is in a nice facility and the other is in a rundown one, results may become effected.

Address concern by:

Try to make the research location the same for both groups.  If this is not possible, the researcher should try and make the facility as simular as they can.

Implementation

Definiton:

The threat to internal validity that happens when research implementers treat both groups differently.  This could be due to two different researchers presenting the information, or one researcher how is excited about one group over another.

Address concer by:

Have a neutral person there to observe the way that the research interacts with both groups to make sure that a implementaiton bias is not happening.

Selection Treatment Interaction

Defintion:

An external threat that occurs when the researcher tries to generalize results of study beyond the groups involved in the study.

Address concern by:
If possible include a random sample research design.  Also, do not generalize research findings beyound study population.

Defintion:

The threat in which the environment conditions or setting under which an experimental study was conducted can be duplicated in other settings.

Address concern by:

Try to incorporate random sampling into research design with simular groups.

Definition:

Threat to external validity when researchers try to generalize findings to past and future situations.

Address concern by:

trying to take into account situiatons that are time limited and how they might effect the research findings.

Defintion:

 When a research project looses participants over a period of time.

Address conern by:

Try to incorporate a large sample size, that way if people drop out of study, it will not effect your results.