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- Occurs when an observed effect of an independent variable on a dependent variable is not caused by extraneous factors.
- If there are alternate explanations for effect on independent variable, internal validity is threatened.
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- The ability to generalize study results to other groups and settings beyond those in current study.
- Research that can be generalized will have more practical value and applications for the researcher.
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- A group of participants exactly like the treatment group with the exception that the control group receives no treatment.
- Valuable for researcher to compare results of treatment group against.
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- The group that receives the experiement or treatment.
- Compared to control group to examine effects of testing.
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- Measurement taken to establish status or level of variable before any experimentation begins.
- Used to measure the effectiveness of a test or program.
- Problems arise when participants learn to test better, effecting the internal validity.
- Differences between pre and post test can be attributed to testing effects and not results from the actual testing.
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- Threatens internal validity when outside events occur between pre and post testing.
- Impossible for researcher to control all elements of stress, natural disaster, current events, illness, etc.
- Depeneding on how study was designed, may be impossible to determine what caused recorded effects.
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- When changes are observed in subject due to elapsed time since study began and may not be the result of any study or testing.
- A control group might eliminate the threat of maturation to internal validity.
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- What a reasearcher uses to collect data.
- There are different instrumentation designs for various kinds of data and research. Well deigned instruments should reduce threat to internal validity.
- Instruments may not be accurate or precise enough to measure what researcher wants to measure.
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- Occurs any time participants are selected for a study using a non-randomized model.
- When selection bias is present, it will reduce internal validity.
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Term
| Selection Maturation Effect |
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Definition
- Occurs when using an intact group that varies in their maturation level.
- Combines weaknesses of maturation and selection bias.
- Prescreening groups on maturity levels may lessen threat to internal validity.
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Term
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Definition
- Occurs when particpants are selected based on exteremly high or extremely low test scores.
- As high testers woud have no where to go but down, and low testers no where but up, internal validity is threatened.
- Randomizing would counter the threat to internal validity.
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Term
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Definition
- Losing participants over time.
- Weakened when participants drop out before study ends.
- Cannot be completely eliminated from reserch, but should be considered within study, to hel pmeasure impact of mortality on future research.
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- A participants personal attitude toward being involved in a study.
- To control for this, researcher should offer comparable treatment to both control and experimental group, insuring that any difference is the result of an intervention and not personal attitudes.
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- Caused by participants expectations rather than any intervention or treatment.
- To control for placebo effect, the researcher should try to provide both the control and experimentation group with the the same information, insuring both groups have similiar expectations.
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- Occurs when treatment supplied to one group spills over and contaminates other groups.
- Researchers should try to study groups with the least amount of day to day contact with each other.
- It is also important to explain to participants the need to keep certain experiments confidential.
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- Occurs when intervention locations differ and have a potential to effect outcome.
- To control for location effect, the reasercher should make all efforts to create identical locations for various groups.
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- Occurs when researcher inadvertently introduces bias or inequality to the study. Often when multiple people are involved in implementation of experiment, with varying levels of knowledge.
- Whenever possible, someone other than program developer should present the program to participants. Pressenter should be as neutral as possible.
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| Selection Treatment Interaction |
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Definition
- First threat to external validity.
- Concerns the degree to which a researcher can generalize the results of a study beyond a specific researched group.
- Whether or not a study is randomized will determine how feasible and ethical it will be to generalize study results.
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| Setting Treatment Interaction |
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Definition
- Second threat to external validity.
- The extent to which environmental conditions can be duplicated in further studies, and in other settings.
- Reducing envionmental differences reduces chances that study results are effected by extraneous factors.
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Term
| History Treatment Interaction |
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Definition
- Third threat to external validity.
- Occurs when reseachers try to generalize findings to past and future situations.
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