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. Author manuscript; available in PMC: 2011 Feb 1.
Published in final edited form as: J Educ Psychol. 2010 Feb 1;102(1):32–42. doi: 10.1037/a0017288

Table 3.

Intraclass Correlations for Change Scores for Same- and Different-Class Twins Pairs (N Pairs in Parentheses; Contrasts Significant at .01 in Bold)

Grades Test MZ pairs DZ pairs

S D S D
K - 1 (152, 189) (141, 201)
Spellinga .70 .54 .45 .50
TOWRE SWE .72 .69 .46 .51
TOWRE PDE .65 .64 .45 .40
1 - 2 (114, 168) (86, 190)
TOWRE SWE .53 .57 .39 .29
TOWRE PDE .46 .43 .29 .30
WRAT
Spelling
.38 .45 .27 .20
WPC .38 .31 .32 .07

Note: S = Same class, D = Different class, TOWRE SWE = Test of Word Recognition Efficiency, Sight Word Efficiency; TOWRE PDE = Test of Word Recognition Efficiency, Phonemic Decoding Efficiency; WRAT Spelling = Wide Range Achievement Test, Spelling; WPC = Woodcock Reading Mastery Test (Revised), Passage Comprehension.

a

In kindergarten the children were assessed with our own spelling test and in Grade 1 with the WRAT Spelling.