single subject and group research design

Single Subject and GroupResearch Design

Terminology

Baseline

Data collected before the start of theintervention, change or experiment

Variability

Frequency and extent to which multiplesmeasures of behavior yield differentoutcomes

A high degree of variability within a givencondition usually indicates that the researcherhas achieved little control over the factorsinfluencing the behavior

Dependent Variable

Target behavior Observed to change in the presence of

the independent variables

Independent Variable

Used to change the targetbehavior/dependent variable

We aim to control the dependent variable byour use of the independent variable

E.g.: If I threw a $5 at you every time youraised your hand, you would probably raiseyour hand frequently. Raising your hand =dependent variable, use of money =independent variable

Changing one variable at atime… Allows us to accurately determine the

variable that is the cause of the change If we change more than 1 variable we

will not be able to say with certaintywhat caused our results

Reversal Design

Repeated measurements of a behavior in agiven setting that requires at least threeconsecutive phases– An initial baseline where the independent variable

is not present– An intervention phase where independent variable

is presented– A return to baseline conditions by removing the

independent variable– (money example)

Irreversible procedure

Some independent variables cannot beremoved

E.g.: Once we have taught a child tosay the word “Help”, we cannot removethe child’s ability to say the word “Help”

In this type of situation we modify ourresearch design

Multiple baseline design

Most widely used Allows researchers to analyze the effects of

the independent variable across multiplebehaviors, settings, subjects

Does not use withdrawal of treatment Used when target behavior is irreversible When withdrawal is undesirable, impractical

or unethical

Validity

Measurement has validity when it yieldsdata that are distinctly relevant to thephenomenon measured and to thereason for measuring it

Variability

Frequency and extent to which multiplesmeasures of behavior yield differentoutcomes

A high degree of variability within a givencondition usually indicates that the researcherhas achieved little control over the factorsinfluencing the behavior

Reliability

A consistent measurement

Clinical Significance

A result that is clinically significant isalso unlikely to have occurred bychance

But a result that is clinically significant isone where the change is of benefit tothe student

The Purpose of Research in BasicScience The discovery of functional relations

among dependent and independentvariables

This knowledge of functionalrelationships become principles thatadd to our knowledge of behavior

The Purpose of Research inApplied Science In ABA the focus is on improving the

lives of individuals through changingproblematic behaviors and increasingappropriate, beneficial behaviors

E.g. Teaching a child to request withPECS may eliminate problematicbehaviors such as self-injury ortantrums.

Example:

Rate of self-injury in student isdecreased from 200x an hour to 150xan hour– Statistically significant

Rate of self-injury in student isdecreased from 200x an hour to 5x anhour– Clinically significant

Group Research Design

Uses a pool of subjects from thepopulation - randomly assigned togroups: experimental group and controlgroup

Results are focused on generality ofresults to general population

Pretest of dependent variable

Single Subject Research Design

Also referred to as single case design Not always 1 subject (four to eight common) Repeated measure of each subject’s behavior are

obtained as she is exposed to each condition of thestudent

Subject often exposed to each conditions severaltimes over the course of an experiment

Measures of the subjects’ behavior during eachphase of the study provide the basis for comparingthe effects of experimental variables as they arepresented or withdrawn in subsequent conditions

Statistical tests may be used butfocus is on socially or clinicallysignificant results - observable,measurable changes; differenttests used

Statistical tests used to rule out“chance”

Data is collected throughoutexperiment

Comparison of pre and postmeasurements

All participants receive treatmentExperimental group receivestreatment, control group doesnot

Results of individual assessedData results are averaged fromall subjects

Measurement of dependent variableconstant throughout study

Initial pretest of dependentvariable done on all subjects

Not randomly assigned forethical reasons

Randomly assigned to group

Specific profiles to suit studySample from population

SingleGroup

So which one is best?

Not a matter of one being better than theother

Rather it is an issue of which is best suited tothe discipline

Behavior analysis is a science focused on theunderstanding and controlling of thebehaviors of the individual

Therefore we primarily use single subjectresearch, with a focus on the repetition ofresults to achieve socially significant behaviorchanges