2 Agenda Overview of Standard Scores Review of Traditional Discrepancy AnalysesContrast Score MethodologyUsing Contrast Score TablesContrast Score InterpretationCase Examples
3 Standard Scores Norm Scores Individual scores are compared to a normative group and establish a person’s ability in relation to othersNorm scores are used to compare an individual to same age peersInterpretation is straightforward, performance is interpreted in relation to norm groupTypically, adjustments are only made for agePerformance is impaired in relation to same age peers
4 Discrepancy AnalysesUsed to determine whether scores are different from one anotherAssist in profile analysisProvides means of interpreting score differences
5 Simple-Difference Discrepancy Analyses Used in WISC-IV, WAIS-IV and WMS-IVObtain a difference by subtracting Score A from Score BCompare the obtained difference using critical values and base ratesA critical value is the minimum required value of a difference in order to obtain statistical significanceThe same critical values are used across ability levels
6 Simple-Difference Discrepancy Analyses Base rates are used to determine if a statistically significant difference is rare and potentially clinically significantBase rates are the frequency with which a specific difference occurred in the normative sampleBase rates are presented as percentages of the overall sample or by ability level bandsThe less frequent the difference in the normative sample, the more clinically relevant it is assumed to be
7 Predicted Difference Discrepancy Analyses Used for WAIS-IV/WMS-IV ComparisonsUses regression methodology to create predicted scoresDifference between predicted and actual scores are compared with critical values and base ratesTypically use linear regression techniques that assume a constant rate of change across ability levelsTypically tails of the distribution produce greater variability in scores so linear techniques underestimate differences at the tails and overestimate differences at the middle range of ability
8 Interpretation of Discrepancy Analyses Difference between 2 scores is equal to or greater than critical value (statistically significant)Johnny’s Working Memory Index and Verbal Comprehension Index are statistically different at the .05 levelBase rates for the difference is 10.4 % in the overall sample and 8.9% by ability levelThe difference occurs in 10.4% of the standardization sample.The difference occurs in 8.9% of the standardization sample at Johnny’s ability level.
9 Contrast Score Overview Introduced by James A. Holdnack (2007)Included within NEPSY-II, WMS-IV, and ACS(Advanced Clinical Solutions for WAIS-IV and WMS-IV will publish in Fall 2009)Contrast scores adjust scores in similar manner as demographically adjusted scoresAdjust one score based on performance on a previous or more basic taskDelayed Memory adjusted for Immediate MemoryRecall Memory adjusted for RecognitionRecall Memory adjusted for RepetitionInhibition adjusted for Naming Fluency
10 Contrast Score Overview Contrast scores yield new normative information on a dependent measure, adjusting for the ability on the control variableContrast score name reflects which variable is control and which is dependentControl variable is listed first in the score title and is used in regression to create the contrast scoreDependent measure is listed second in the title and the derived contrast score reflects performance on this measureExamplesControl vs. Dependent Contrast Scaled ScoreAuditory Attention vs. Response Set Contrast Scaled scoreLogical Memory Immediate Recall vs. Delayed Recall
11 Contrast Score Overview Scored on 1-19 Scaled Score MetricDoes not replace normative scoresAnswer’s specific hypothesis about an examinee’s performance relative to their performance on other measuresNorm score asks: Is this person’s delayed memory impaired?Contrast score asks: Is this person’s delayed memory impaired given their initial encoding ability?
13 Contrast Score Interpretation Higher scores indicate better than expected performance on the dependent score given performance on the control scoreDelayed Memory is better than expected given the examinee’s level of ability on immediate memoryDelayed Memory is superior when compared to individuals of similar encoding ability
14 Contrast Score Interpretation Low scores indicate poorer than expected performance on the dependent score given performance on the control scoreDelayed Memory is impaired given the examinee’s level of ability on immediate memoryDelayed Memory is impaired when compared to individuals of similar encoding ability
15 Contrast Score Interpretation Scores in the average range (8-12) indicate no difference in performance between the control and dependent measuresPerformance on delayed memory is not significantly different from ability on immediate memoryDelayed Memory performance is similar to encoding ability
16 Contrast Scores Case Examples Normative ScoresJoe obtains a 6 on VR I and a 6 on VR IIInterpret VR I and VR II as impaired in comparison to his same age peersSimple Difference Discrepancy AnalysisVR I (6) – VR II (6) = 0Difference is not statistically significantFinal Interpretation Using Simple DifferenceBoth VR I and VR II are impaired but are not significantly different from one anotherSuggested InterventionTarget interventions toward both encoding and retrieval deficits
17 Contrast Scores Case Examples Normative ScoresJoe obtains a 6 on VR I and a 6 on VR IIContrast ScoreVR I vs. VR II Contrast Scaled Score is 8Final Interpretation Using Contrast Scaled ScoreIn relation to his peers, both immediate and delayed memory are impaired. Contrast score shows that VR Delayed is actually within average (SS=8) when adjusted for his immediate ability. His delayed memory performance is being impacted by his immediate memory ability. Thus, his critical memory problem may be in initial encoding ability.Suggested InterventionTarget intervention toward encoding difficulties
18 Contrast Scores Case Examples Normative ScoresJoe gets all items correct on recognition (>75%) and obtains an 8 on LM II Delayed RecallInterpret Recognition as above average and LM II as average in comparison to same age peersSimple Difference DiscrepancyCan’t complete as both scores are not on same metricFinal Interpretation Using Simple DifferenceCompared to same age-peers, recognition performance is above average and delayed recall performance is averageSuggested InterventionNo intervention is needed
19 Contrast Scores Case Examples Normative ScoresJoe gets all items correct on recognition (>75%) and obtains an 8 on LM II Delayed RecallContrast ScoreLM Recognition vs. LM II Contrast Scaled Score is 6Final Interpretation Using Contrast Scaled ScoreCompared to same age-peers, recognition performance is above average and delayed recall performance is average. Contrast Score demonstrates that recall is unexpectedly low for his recognition ability. His performance appears to be impacted by his retrieval ability. Thus, his critical memory problem may be in memory retrieval or expressive language ability.Suggested InterventionAssess expressive language, target intervention toward retrieval difficulties
20 Contrast Scores Case Examples Example 3 (General Ability vs. Delayed Memory)Normative ScoresJoe obtains GAI of 120 and DMI of 100Interpret GAI of 120 as superior and DMI of 100 as averageSimple Discrepancy AnalysisGAI (120) – DMI (100) = 20Difference is statistically significant; base rate of 5-10%Final Interpretation Using Simple DifferenceDMI is significantly lower than GAI and a difference this large occurs in less than 10% of the standardization sample. Both skills are average compared to same age peers but delayed memory is relatively weak in comparison to general cognitive abilitySuggested InterventionIf any intervention is needed, focus on delayed memory abilities
21 Contrast Scores Case Examples Normative ScoresJoe obtains GAI of 120 and VMI of 100Contrast ScoreGAI vs. DMI Contrast Scaled Score is 7Final Interpretation Using Contrast Scaled ScoreContrast Score shows that his DMI score is low average given his general cognitive ability.Suggested InterventionTarget intervention on delayed memory abilities
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