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Table 4 Contrast codes for models

From: An item response theory approach to longitudinal analysis with application to summer setback in preschool language/literacy

T Contrasts T 1 T 2 T 3 T 4
   P Fall 1 0 0 0
  P Spring 0 1 0 0
   K Fall 0 0 1 0
  K Spring 0 0 0 1
C Contrasts C 1 C 2 C 3 C 4
   P Fall 1/2 0 1/2 −1/√2
  P Spring 1/2 −1/√2 −1/2 0
   K Fall 1/2 1/√2 −1/2 0
  K Spring 1/2 0 1/2 1/√2
  1. Note. The contrasts in Model 2 are labeled as: C1 is the average ability; C2 is the summer effect; C3 is the overall change; and C4 represents the increment in growth rate from preschool to kindergarten.