Experimental Control Definition Is a predictable change in behavior (dependent variable) that can be...
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Transcript of Experimental Control Definition Is a predictable change in behavior (dependent variable) that can be...
Experimental Control Definition
Is a predictable change in behavior (dependent variable) that can be reliably produced by the systematic manipulation of some variable (independent variable)
Goal of Behavior Analysis
1. Experimentally determine the effects of environmental manipulation on behavior
2. and demonstrate the effects can be reliably produced
Internal Validity
The extent to which an experiment shows that changes in behavior are a function of the independent variable
and not the result of uncontrolled or unknown variables
Problem: Confounding Variables
Variables known or suspected to exert an uncontrolled influence on the dependent variable
Effects must be evaluated and eliminated to demonstrate experimental control
Problem:May not know all of the confounding variables
Time of day Barometric pressure Other unknown
Solution
Eliminate as many uncontrolled variables as possible
OR
Hold constant the influence of all other variables except the independent variable
Behavior
Can be an individual phenomenonCan be a continuous phenomenonAssumes That:
Behavior is determinedBehavioral variability is extrinsic to the
organism
Behavior as an Individual Phenomenon
Examine a person’s interaction with the environment
With ABA Strategy often based on within-subject (single-
subject) designs
Contrast: Dynamic / Continuous Behavior Behavior changes over time Requires continuous measurement over time
• Complete record of behavior as it occurs in context• Often uses cumulative recorder types of
methodologies for recording• Systematic repeated measurement is the “hallmark” of
ABA
Assumes
1. The occurrence of any event is determined by the functional relations it holds to other events
2. Behavior is a natural phenomenon
3. Behavioral variability is the result of some environmental influence
• In ABA• Try to find out what it is• Try to find interventions to change the
behavior
Components of Experiments in ABA
• Examine at least one– Subject or participant– Behavior (dependent variable)– Setting– Treatment or intervention condition (independent
variable)
Research Question(s)
Are statements about what the person wants to learn about a behavior by conducting an experiment.
Specifically: What are the effects of the independent variable on the dependent variable
Are always written down: Nothing exists until it is on paper (Brigham) Allows you to identify what you are examining Allows you to identify problems Allows you to create solutions
Many Different DesignsGroup DesignsSingle SubjectMultiple BaselineSimultaneous Treatment OthersEach has its advantages and disadvantages.Past research and experience helps you
decide on the type of design to use
Experiment using GroupsRandomly selected pool of subjects from
relevant populationDivided into experimental and control groupsPretest, application of independent variable
to experimental group, and posttest
Problem
Group data may not be representative of individual performanceSome individuals within a group may stay the
same or decrease, while the improvement of others could make it appear as overall average improvement
To be most useful, treatment must be understood at an individual levelIndividual can mean a group in an organization
Group Data Masks VariabilityHides variability that occurs within and
between subjectsUse statistical control to compensateShould not be a substitute for experimental
control
To control effects of any variable, must either hold it constant or manipulate it as an independent variable
ABA Often uses single-subject designs Subject becomes its own control
Measures of the subject’s behavior during each phase of the study
Allows you to compare variables as they are presented or withdrawn during various conditions
May have Single or Multiple Dependent Variables
• Single• Only manipulation one variable• Can often see clear results
• Multiple • Still manipulate one variable• Have multiple dependent variables
ReasonsGives data patterns that can serve as controls when
evaluating & replicating the effects of an independent variable
Allows you to assess the presence or extent an independent variable may effect behaviors other than the response class.
Allows you to determine whether changes in behavior of others occur during the course of an experiment Changes may explain changes in the subject’s
behavior
Measurement Systems and Visual Analysis
• Observation & recording procedures must be conducted in a standardized manner
• Standardization involves every aspect of the measurement system– Definition of the target behavior to scheduling of
observations
• Behavior analysts must develop skills in the detection of changes in the level, trend, and degree of variability in behavioral data
Independent and Dependent Variables
– Independent Variable– The aspect of the environment that the experimenter
manipulates – The researcher controls or manipulates this variable
independent of the subject’s behavior or any other event
– Dependent Variable– The behavior that changes as a result of changes in
the independent variable– Is the thing you are observing
Experimental design
• Nonparametric study– Independent variable is either presented or absent
during a time period or phase of the study
• Parametric study– The value of the independent variable is manipulated– Seeks to discover the differential effects of a range of
values
Fundamental Rule in Experimental Designs
• Change only one variable at a time– Experimenter can attribute any measured changes to
a specific independent variable– If investigating the effects of a “treatment package”
• Ensure that the entire package is presented or withdrawn each time a manipulation occurs
• Allows you to make causal statements
Some Additional Rules
• Do not get locked into textbook “designs”• Select & combine experimental tactics that best
fit the research questions
Steady State Strategies
– Repeated exposure of a given subject to a given condition
– Try to eliminate or control extraneous influences on behavior & obtaining a stable pattern of responding before introducing the next condition
Baseline Data in ABA
• Serves as a control condition• Does not imply the absence of intervention
– Absence of a specific independent variable
• Why examine?– Allows you to observe a level of responding in the
absence of an independent variable – Allows you to make comparisons when you
introduce an intervention
Benefits
• You can obtain descriptions of antecedent-behavior-consequent correlations for the planning of an effective treatment
– Valuable guidance in setting initial criteria for reinforcement
– Baseline data may reveal the behavior targeted for change does not warrant intervention
Types of Baseline Data Patterns
• Stable baseline (A)• Ascending baseline (B and C)• Variable baseline (D)
Types of Baseline Data Patterns
Example
ProblemMay be due to other variables
Need Verification
• Done by termination or withdrawal of the treatment variable
Verification
Can use Replication
ConclusionsLots of aspects to experimental designsNeed to make sure you know the strengths
and weaknesses of the designs you plan to use.
Want to ensure your conclusions are based on solid data.