Case Study: Marcus Marcus, age 9 years 8 months, is in the fourth grade and is having some academic difficulties in school. He was administered the Stanford Achievement Test, Tenth Edition (Stanford 10). Based on Marcus' scores on the summary report, answer the following questions: Stanford 10 Student Summary Report National Grade Percentile Bands Numbe Numbe Nationa Nationa Grade AAC Possibl d I PR-S' I NCE Equivale Range Subtests and Total Correct Score nt 1 10 30 50 70 Total Reading 114 82 539 59-5 54.6 5.4 Middle Total Mathematics 29 629 22-3 33.7 3.3 Low Language 610 39-4 44.1 3.5 Middle Spelling 30 647 73-6 62.9 6.4 High Science 310 18-3 30.7 2.8 LOW Social Science 607 40-5 44.7 3.5 Middle Listening 77 35-4 41.9 Middle Complete Battery 402 270 56-5 53.4 5.0 Middle "PR-S: Percentile Rank and Stanine 1. Interpret the percentile ranks (PR) for each of the subtests and total score. 2. Interpret the stanine scores (S) for each subtest and total score. 3. Across subtest and total scores, identify Marcus' relative strengths and weaknesses based on his stanine (S) scores. 4. The percentile bands provide a graphic display of measurement error. The wider the bands, the more error on the subtests. a. Which subtest score(s) appear to have the greatest error? b. Which subtest score(s) appear to have the least error? 5. Marcus' grade equivalent score on spelling is 6.4. Based on this score, Marcus' parents believe he is ready for instruction in spelling at the 6th grade level. Do you agree with this? Why or why not