2. GENERALIDADES
2.5 MARCO REFERENCIAL
2.5.1 MARCO TEÓRICO
Measures from previous TEDS assessments, their validity, and administration procedures are described in detail in previous TEDS publications (e.g., Kovas et al., 2007a; Haworth et al., 2009). The following paragraphs provide only a brief outline of each measure analysed for the purposes of this thesis.
2.4.1.1 Measures at 7 years
Cognitive ability measures at 7 were collected using telephone testing. Children mathematical school achievements were derived from the teacher’s questionnaires.
Verbal Ability: A composite measure was obtained from the Wechsler Intelligence Scale for Children (WISC-III) Vocabulary test and the WISC-III Similarities test (Wechsler, 1992).
Non-Verbal Ability: A composite measure was obtained from the test of Conceptual Grouping (McCarthy, 1972) and WISC Picture Completion test (Wechsler, 1992). Reading Ability: Composite of fluency reading was obtained from scores of the two TOWRE (Test of Word Reading Efficiency) sub-tests - the Test of Sight Word Efficiency (non-words) and the Phonemic Decoding Efficiency test (words) - (Torgesen, Wagner, & Rashotte, 1999).
Mathematical Achievement: Teachers assessed children’s achievement, based on the expected UK standard at Key stage 1 (QCA-Qualifications and Curriculum Authority Key stage-1 www.qca.org.uk/ca/tests) on three mathematical components: "using and applying mathematics", "numbers", "shapes, space and measures". The composite score of the three assessments was used.
2.4.1.2 Measures at 9 years
Data for this wave of testing was collected by postal booklets. The cognitive measures were derived from the child-completed booklets; the mathematical scores were derived from the teachers’ questionnaires.
Verbal Ability: The verbal cognitive score was obtained from the Vocabulary Multiple Choice and General Knowledge tests taken from WISC-III-PI (Kaplan et al., 1999). Non Verbal Ability: The non verbal cognitive score was derived from scores of two tests: the “Puzzle” and “Shapes” tests adapted from Smith, Fernandes, & Strand, (2001).
Mathematical Achievement: Teachers assessed children’s achievement, based on the expected UK standard at Key stage-2 (QCA Key stage-2) on three mathematical components: "using and applying mathematics", "numbers and algebra", "shapes, space and measures". A composite of the three mathematical scales was used.
2.4.1.3 Measures at 10 years
Data at 10 years were collected using a web-based battery of cognitive tests and mathematical performance. An additional measure of mathematical school achievement was available from the teachers’ questionnaire.
Verbal Ability: The verbal ability scale was derived combining the Vocabulary Multiple Choice and the General Knowledge web-tests from the WISC-III-PI (Kaplan et al., 1999).
Non Verbal Ability: The scale was obtained from two web tests: Picture Completion (Wechsler, 1992) and the Raven Standard Progressive Matrices (Raven et al., 1996). Reading Ability: Reading ability was assessed with the web-test of reading comprehension PIAT (Peabody Individual Achievement test; Markwardt, 1997).
Mathematics Web Test: The test was based on the items of the NFER 5–14 Mathematics Series. The mathematics web score was derived combining together 3 tests assessing the mathematical sub-components: "non-numerical processes", "understanding numbers", "computation and knowledge".
Mathematical Achievement: Mathematical school achievement was assessed by teacher questionnaires based on the standards required from the UK National Curriculum at Key Stage 2 (QCA Key Stage-2) on the mathematical components of: "using and applying mathematics", "number and algebra" and "shapes, space and measures".
2.4.1.4 Measures at 12 years
Data at 12 years were collected using a web-based battery of cognitive tests and mathematical performance. An additional measure of mathematical school achievement was available from the teachers’ questionnaire.
Verbal Ability: The verbal ability scale was derived from Vocabulary Multiple Choice and General Knowledge web-tests from the WISC-III- PI (Kaplan et al., 1999).
Non Verbal Ability: The composite score of non verbal ability was obtained from two non-verbal reasoning web-tests: Raven’s Standard Progressive Matrices (Raven, Court, & Raven, 1998) and the Picture Completion Test (Wechsler, 1992).
Reading Ability: Reading ability was assessed with 3 tests of reading fluency and 2 tests of reading comprehension: TOWRE, reading fluency of words and non-words (administered on the phone) (Torgesen, Wagner, & Rashotte, 1999); Woodcock- Johnson III Reading Fluency Test (Woodcock et al., 2001); GOAL-Reading comprehension–Formative Assessment in Literacy - Key Stage 3 (GOAL plc, 2002); PIAT- Reading comprehension-Peabody Individual Achievement Test (Markwardt, 1997). The scores of the 5 tests were combined together in a composite reading score.
Language Ability: A composite score was obtained from three web-tests: Figurative Language - the test of semantic language competences (Wiig et al., 1989); Inferences – the test assessing pragmatics skills (Wiig et al., 1989); and TOAL-3 - the test of grammar (Hammill et al., 1994).
Spatial Ability: A composite score was obtained from the “Hidden Shapes” and the “Jigsaw” web-tests, both taken from the nferNelson Spatial Reasoning Series books (nferNelson, 2002).
Mathematics Web test: The test was based on the nferNelson 5–14 Mathematics Series. A composite score was created from scores on the three mathematical components: "understanding numbers", "non-numerical processes", "computation and knowledge" (nferNelson, 1994; 1999).
Mathematical Achievement: Mathematics was assessed by teacher questionnaires that rated the twins' school achievement on four mathematical components: "using and applying mathematics", "number and algebra", "shape, space and measures", "handling data". The rating was based on the requirement levels set by UK National Curriculum and taken from the booklets Mathematics 5-14 of the National
Foundation for Educational Research (nferNelson, 1999).
2.4.1.4 Measures at 14 years
Data uses in the analyses at 14 years were collected using a web-based battery of cognitive tests. The measure of mathematical school achievement was available from the teachers’ questionnaire. Scores of the Language test obtained by phone were not used in the longitudinal analyses.
Verbal Ability: The verbal ability scale was derived from Vocabulary Multiple Choice and General Knowledge from the WISC-III- PI (Kaplan et al., 1999).
Non Verbal Ability: The non verbal ability was measured by the Raven’s Standard Progressive Matrices test (Raven et al., 1998).
Mathematical Achievement. Teachers rated the twins mathematical school achievement according to the levels required from the UK National Curriculum on four components: "using and applying mathematics", "number and algebra", "shape, space and measures", "handling data". Teachers' questionnaire was based on the booklets Mathematics 5-14 of the National Foundation for Educational Research (nferNelson, 1999).