Computerized Adaptive Testing

1
Reducing the duration and cost of assessment with
the GAIN Computer Adaptive Testing
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Evidence-Based Practice

• Requires accurate diagnosis, treatment placement,
  and outcomes monitoring
• Assessment over a wide range of domains
• The cost of evidence-based assessment is
• Time
• Respondent Burden
• Increased staff resources (including training

3
Improving Efficiency

• The use of screeners and short-form instruments
  has significantly improved the efficiency of the
  assessment process
• Can help determine whether a full assessment is
  warranted
• But not a substitute for a full assessment
• Lack of precision
• Floor and ceiling effects
• Limited content validity

4
Computerized Adaptive Testing

• Selects items from a large bank of items based on
  the responses made to previous items.
• Continues to select and administer items until
  sufficient measurement precision is obtained.
• Combines the precision and comprehensiveness of a
  full assessment with the efficiency of a screener.

5
CAT Process
Typical Pattern of Responses
Increased Difficulty

• Score is calculated and the next best item is
  selected based on item difficulty

Middle Difficulty
/- 1 Std. Error
Decreased Difficulty
Correct
Incorrect
6
CAT in Clinical Assessment
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CAT in Clinical Assessment Issues

• Triage of individuals to support clinical
  decision making

• Measurement of multiple clinical dimensions and
  subdimensions

• Persons with atypical presentation of symptoms

• Generalizability of assessment to various groups

8
Clinical Decision Making

• How severe are the symptoms?
• What type of treatment is most appropriate?
• Can CAT be used to answer these questions more
  efficiently?

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Strategy

• Use CAT to place persons into low, moderate and
  high levels of substance abuse and dependency.
• Starting Rules
• Using screener measures to set the initial
  measure and select the first item
• Variable Stop Rules
• Tight precision around cut points
• Less precision away from cut points

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CAT Standard Error
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Results

• CAT to full-measure correlations ranged from .87
  to .99
• Classification of persons into treatment groups
  based on CAT and full measure (kappa
  coefficients) ranged from .66 to .71.
• Screener starting rule improved CAT efficiency by
  7 percent
• Variable stop rules improved efficiency by 15-38

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Measuring Multiple Dimensions
13
Assessment on Multiple Dimensions

• Instruments often measure multiple domains
• In CAT, treating a multi-domain measure as
  measuring one domain is problematic
• Some subdimensions may not be adequately measured

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Strategy Content Balancing

• Set an item quota for each subscale
• Maximum number of subscale items to administer
  during the CAT
• An item is selected if
• Its subscale quota has not been met
• Provides maximum information

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Content Balancing Procedures
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Percentage of Items Administered by Subscale
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Cont. Balancing CAT to Full IMDS Correlations
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Identifying Persons with Atypical Presentation of
Symptoms
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Overview

• Implications Clients sometimes endorse severe
  clinical symptoms that are not reflected by
  overall scores on standard assessments.
• Statistics that can detect atypical presentation
  of symptoms have important clinical implications.
  
• Strategy Identify fit statistics sensitive to
  atypical presentation in a CAT context

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Rasch Fit Statistics

• Fit statistics are used to test particular
  hypotheses.
• Atypicalness Used to detect unexpected outlying,
  off-target responses. Outlier sensitive
• Example A person with a high level on the
  measured trait misses an easy item.
• Randomness Used to detect unexpected inlying,
  targeted responses.
• Both infit and outfit are chi-square statistics.
  An infit or outfit value of 1.0 indicates perfect
  fit to the Rasch model.

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Problems with Fit
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Clinical Implications of Misfit

• Our analyses indicate that there are subgroups
  who endorse severe symptoms without endorsement
  of milder symptoms.
• Examples
• Atypical suicide
• Substance use withdrawal without dependence

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Atypicalness by Number of Items
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Content Balancing and Atypicalness
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Future Research

• Identify alternative fit statistics that are more
  sensitive to atypical presentation of symptoms
• Determine when it is likely that someone may be
  present with atypical symptoms, and if so, select
  items to confirm atypicalness.

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Generalizability of CAT to Various Groups
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Overview

• Persons at the same severity level may differ in
  their endorsement of specific items.
• This is called differential item functioning
  (DIF)
• On the GAIN, DIF has been detected by
• Age (adolescent vs. adult)
• Gender
• Ethnicity/Race
• Drug of choice

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DIF By GAIN Scale
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DIF and CAT

• The presence of DIF can limit our ability to
  generalize measurement findings across different
  groups.
• Controlling for DIF becomes complicated as the
  number of DIF items and groups/factors increases.
  
• Currently exploring a number of methods for
  controlling DIF in CAT.

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Potential of CAT in Clinical Practice

• Reduce respondent burden
• Reduce staff resources
• Reduce data fragmentation
• Streamline complex assessment procedures
• Assist in clinical decision making
• Identify persons with atypical profiles
• Improve measurement generalizability

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Future Research

• How do we put it all together?
• Much of the research in the area of CAT has used
  computer simulation. There is a need to test
  working CAT systems in clinical practice.

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Contact Information

• A copy of this presentation will be at
  www.chestnut.org/li/posters
• For more information, please contact Barth Riley
  at bbriley_at_chestnut.org