1. Basic Assessment Principles Chapter 2

2.  Nominal  Ordinal  Interval  Ratio Measurement Scales

3.  Individual’s score is compared to performance of others who have taken the same instrument (norming group)  Example: personality inventory  Evaluating the norming group  size  sampling  representation Norm-Referenced Instruments

4.  Individual’s performance is compared to specific criterion or standard  Example: third-grade spelling test  How are standards determined?  common practice  professional organizations or experts  empirically-determined Criterion-Referenced Instruments

5. Robert 72 Miles 96 Jason 68 Whitney 79 Alice 82 Paul 59 Pedro 86 Jane 85 Beth 94 John 82 Kelly 92 Michael 81 Amy 77 Kevin 85 Justin 72 Rebecca 88 Porter 62 Ling 98 Sherry 67 Maria 86 Norm-Referenced: Sample Scores

6. Frequency Distribution

7. Frequency Polygon

8. Histogram

9. Measures of Central Tendency  Mode – most frequent score  Median – evenly divides scores into two halves (50% of scores fall above, 50% fall below)  Mean – arithmetic average of the scores  Formula:

10. Measures of Central Tendency Example: Sample scores – 98, 98, 97, 50, 49  Mode = 98  Median = 97  Mean = 78.4

11. Measures of Variability  Range – highest score minus lowest score  Variance – sum of squared deviations from the mean  Standard Deviation – square root of variance  Formula:

12. Normal Distribution

13. Skewed Distribution

14.  Raw scores  Percentile scores/Percentile ranks  Standard scores  z scores  T scores  Stanines  Age/grade-equivalent scores Types of Scores

15. Percentiles

16.  98 th percentile  98% of the group had a score at or below this individual’s score  32 nd percentile  32% of the group had a score at or below this individual’s score  If there were 100 people taking the assessment, 32 of them would have a score at or below this individual’s score Interpreting Percentiles

17.  Units are not equal  Useful for providing information about relative position in normative sample  Not useful for indicating amount of difference between scores Interpreting Percentiles

18. Types of Standard Scores

19. z Scores  z score = X-M s  Mean = 0  Standard deviation = 1

20.  Mean = 50  Standard deviation = 10 T Scores

21. Stanines

22. Standard Scores: Summary

23.  Possible problematic scores  Age-equivalent scores  Grade-equivalent scores  Problematic because:  These scores do not reflect precise performance on an instrument  Learning does not always occur in equal developmental levels  Instruments vary in scoring Additional Converted Scores

24.  Adequacy of norming group depends on:  Clients being assessed  Purpose of the assessment  How information will be used  Examine methods used for selecting group  Examine characteristics of norming group Evaluating the Norming Group

25.  Methods for selecting norming group:  Simple random sample  Stratified sample  Cluster sample Sampling Methods

26.  Size  Gender  Race/ethnicity  Educational background  Socioeconomic status  Is the norming group appropriate for use with this client? Norming Group Characteristics