Research – Internal/External Validity Flashcards
_____ is the extent to which it’s possible to derive accurate conclusions from the results about the nature of the relationship between the study’s independent and dependent variables.
Internal validity
______ is the extent to which it’s possible to generalize those conclusions to other people and conditions.
External validity
What are the seven threats to internal validity?
- History
- Maturation
- Differential Selection
- Statistical regression
- Testing
- Instrumentation
- Differential attrition
Her Majesty’s Differing Statements Tell of Interesting Developments
How does history affect internal validity?
History refers to events that occur during the course of a study and are not part of the study but affect its results. The best way to control history when it’s due to events that occur outside the context of the study is to include more than one group and randomly assign participants to the different groups.
How does maturation affect internal validity?
Maturation refers to physical, cognitive, and emotional changes that occur within subjects during the course of the study that are due to the passage of time and affect the study’s results. The longer the duration of the study, the more likely its results will be threatened by maturation. The best way to control maturation is to include more than one group in the study and randomly assign participants to the different groups
How does differential selection affect internal validity?
Differential selection is a misnomer because it actually refers to differential assignment of subjects to treatment groups. It occurs when groups differ at the beginning of the study due to the way they were assigned to groups and this difference affects the study’s results. The best way to control differential selection is to randomly assign participants to groups so the groups are similar at the start of the study.
How does statistical regression affect internal validity?
Statistical regression is also known as regression to the mean and threatens a study’s internal validity when participants are selected for inclusion in the study because of their extreme scores on a pretest. It occurs because many characteristics are not entirely stable over time and many measuring instruments are not perfectly reliable. Statistical regression is controlled by not including only extreme scorers in the study or by having more than one group and ensuring that the groups are equivalent in terms of extreme scorers at the beginning of the study.
How does testing affect internal validity?
Testing threatens a study’s internal validity when taking a pretest affects how participants respond to the posttest. This threat is controlled by not administering a pretest or by using the Solomon four-group design, which is described below.
How does instrumentation affect internal validity?
Instrumentation is a threat to internal validity when the instrument used to measure the dependent variable changes over time. For example, raters may become more accurate at rating participants over the course of the study. The only way to control instrumentation is to ensure that instruments don’t change over time. If that’s not possible, its potential effects must be considered when interpreting the study’s results.
How does differential attrition affect internal validity?
Differential attrition threatens internal validity when participants drop out of one group for different reasons than participants in other groups do and, as a result, the composition of the group is altered in a way that affects the results of the study. Attrition is difficult to control because researchers often don’t have the information needed to determine how participants who drop out from a study differ from those who remain.
What are the four threats to external validity?
- Reactivity
- Multiple treatment interference
- Selection-treatment interference
- Pretest-treatment interference
How does reactivity affect external validity?
Reactivity might cause participants to respond differently to the IV than they normally would.
- Demand characteristics are cues that inform participants of what behavior is expected of them.
- Experimenter expectancy occurs when the experimenter acts in ways that bias the results of the study and can involve (a) actions that take the form of demand characteristics and directly affect participants (e.g., saying “good” whenever a participant gives the expected or desired response) or (b) actions that don’t directly affect participants (e.g., recording the responses of participants inaccurately in a way that supports the purpose of the study).
How does multiple treatment interference affect external validity?
Multiple treatment interference is also referred to as carryover effects and order effects. It may occur whenever a within-subjects research design is used – i.e., when each participant receives more than one level of the independent variable.
How does selection-treatment interference affect external validity?
A selection-treatment interaction is a threat to external validity when research participants differ from individuals in the population, and the difference affects how participants respond to the independent variable. For example, people who volunteer for research studies may be more motivated and, therefore, more responsive to the independent variable than non-volunteers would be. The best way to control this threat is to randomly select subjects from the population.
How does pretest-treatment interference affect external validity?
A pretest-treatment interaction is also known as pretest sensitization and threatens a study’s external validity when taking a pretest affects how participants respond to the independent variable. For example, answering questions about a controversial issue in a pretest may make subjects pay more attention to information about that issue when it’s addressed in a lecture or discussion during the study.
