Internal Validity Flashcards
Observed relationship between two or more variables should remain unambiguous as to what it means rather than being due to “something else”
Internal Validity
observed differences on the dependent variable are directly related to the independent variables and not due to some other unintended variable
Internal Validity
Selection of people for a study may result in the individual differing from one another in unintended ways
Subject Characteristics
Subject Characteristics is sometimes referred as
Selection bias/Subject characteristics threat
Loss of subject is also known as
mortality threat
When subjects or individuals drop out for one reason or another
Loss of Subject
true in most intervention studies since they they take place and time
Loss of Subject
A problem in questionnaire studies
Failure to complete instruments
Loss of subjects not only limits generalizability but also
introduce bias
A common misconception in loss of subject
that threat can be eliminated simply by replacing the subject
Attempt to eliminate the problem of mortality
provide evidence that the subjects lost were similar to those remaining on pertinent characteristics
Particular location in which data is collected or in which intervention is carried out
Location
the best method of control for location threat is
hold location constant (keep it same for all participants)
the way instruments are used may also constitute a threat to internal validity
Instrumentation
Alternative name for instrumentation threat
Instrumentation decay
Often the case when the instrument permits different interpretation results resulting in fatigue of the scorere
Instrumentation
Principal way to control instrumentation decay
schedule data collection and/or scoring
Demographic (age, gender, etc.) of the individual who collects the data in the study and how it may affects the nature of the data collected
Data collector characteristics
primary ways to control data collector characteristics
using the same data collector(s) throughout, analyzing data separately for each collector
data collector or scorer may unconscious distortion of data in ways to make certain outcomes more likely
Data collector bias
two principal techniques for handling data collector bias
Standardize procedures (require some sort of training) Collector lacks information
means the use of any form of instrumentation, not just “test”
Testing
Common practise before and after interventions
Testing
One of more unanticipated or unplanned evers may occur which can affect responses of subjects
History
Change during an intervention due to factors associated rather with the passing of time rather than the intervention itself
Maturation
a serious threat only in studies using pre-post data for the intervention group, or in studies that span a number of years
Maturation
best way to control for Maturation
include a well-selected comparison group
How subjects view a study and participate in it
attitude of subjects
Hawthorne effect was first observed in
Hawthorne plant of Western Electric Company
Special attention and recognition improved performance because they felt someone cared for them. This positive effect, resulting from increased attention and recognition of subjects
Hawthorne Effect
One remedy for Hawthorne Effect is to provide
the control or comparison group with a special or novel treatment
Threat may be present whenever change is studied in a group that is extremely low or high in its pre intervention performance
Regression
can describes the fact that a group because of unusually low or high performance will, on the average score closer to the mean on subsequent testing, regardless of what transpires in the meantime
Regression
Treatment or method in any experimental study must be administered by a selected individual
Implementation
Implementation can occur when
- different individuals are assigned to implement diff. methods
- individuals have a personal bias in favor of one method over the other
How to reduce threats to internal validity?
- Careful planning
2. Planning requires collecting additional information
