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Large-scale Assessments in Education

An IERI – International Educational Research Institute Journal

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.
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