Appendix A: Summary of variables included in the Outcome Index

Infant cohort

Physical

Overall health rating: single parent rated item of infants' health, from 1 (excellent) to 5 (poor).
Special health care needs: single derived yes or no item based on six component items indicating whether child needed medication or more health care than the average child due to a condition that has lasted or was expected to last 12 months or more.

Social–emotional

STSI Approach: mean of a four item parent rated subscale from abbreviated Short Temperament Scale for Infants (STSI) (Sanson et al. 1987; Prior et al. 2000) on 1 to 6 frequency scale; low scores indicate withdrawing/shy, and high scores indicate approaching/sociable; response rate 84 per cent; adequate reliability (alpha=0.72).
STSI Irritability: mean of a four item parent rated subscale from abbreviated STSI, on 1 to 6 frequency scale; low scores indicate calm/not irritable, and high scores indicate irritable/volatile; response rate 84 per cent; fair reliability (alpha=0.57).
STSI Cooperativeness: mean of a four item parent rated scale from abbreviated STSI, on 1 to 6 frequency scale; low scores indicate uncooperative, unadaptable, and high scores indicate adaptable, cooperative; response rate 84 per cent; adequate reliability (alpha=0.65).

Learning

CSBS total: normed standardised score based on 24 items in the parent report Communication and Symbolic Behaviour Scale (Wetherby & Prizant 2001); items reflect the child's exhibition of various behaviours demonstrating emerging communication skills; good reliability (alpha=0.89).

Physical

Health

Overall health rating: single parent rated item of child's health, from 1 (excellent) to 5 (poor).
Special health care needs: single derived yes or no item based on six component items indicating whether child needed medication or more health care than the average child due to a condition that has lasted or was expected to last 12 months or more.
Body Mass Index (BMI): calculated from directly assessed variables of child's height and weight.

Motor

PedsQL Physical Health Summary score: eight item parent report scale from the PedsQL (Varni, Seid & Rode 1999), assessing the physical functioning dimension of the broader health related quality of life construct. Essentially, it assesses a child's level of functioning in daily activities that rely on good physical health. Scaled to range from 0 (poor) to 100 (good).

Social–emotional

Social competence

SDQ Prosocial: mean of five parent rated items in the Prosocial subscale of the Strengths and Difficulties Questionnaire (SDQ) (Goodman 1997), assessing the child's propensity to behave in a way that is considerate and helpful to others, with items scored from 1 (not true) to 3 (certainly true); adequate reliability (alpha=0.66).
SDQ Peer problems: mean of five parent rated items in the Peer subscale of the SDQ, assessing problems in the child's ability to form positive relationships with other children, with items scored from 1 (not true) to 3 (certainly true); fair reliability (alpha=0.50).

Internalising

SDQ emotional symptoms: mean of five parent rated items in the Emotional Symptoms subscale of the SDQ, assessing a child's frequency of display of negative emotional states (for example, nervousness, worry) with items scored from 1 (not true) to 3 (certainly true); fair reliability (alpha=0.58).

Externalising

SDQ Hyperactivity: mean of five parent rated items in the Hyperactivity subscale of the SDQ, assessing child's fidgetiness, concentration span and impulsiveness with items scored from 1 (not true) to 3 (certainly true); good reliability (alpha=0.74).
SDQ Conduct: mean of five parent rated items in the Conduct subscale of the SDQ, assessing child's tendency to display problem behaviours when interacting with others, with items scored from 1 (not true) to 3 (certainly true); good reliability (alpha=0.69).

Learning

Language

PPVT: A standardised Rasch modelled score based on interviewer administration of an abbreviated form of the Peabody Picture Vocabulary Test (PPVT-III Form IIA) (Dunn & Dunn 1997), a measure of receptive language.

Literacy

Parent rating of reading skills: parent rating on three yes/no items assessing whether a child has obtained reading skills at different levels of complexity, summed to give scores from 0 (good) to 3 (poor).
Teacher rating of reading skills: teacher yes/no ratings on five items; 0 (poor skills) to 5 (strong skills); available for 64 per cent of sample. Items assess the level of complexity a child is capable of reading as well as the child's interest in reading.
Teacher rating of writing skills: teacher yes/no ratings on six items; 0 (poor skills) to 6 (strong skills); available for 65 per cent of sample. Items assess the level of complexity of the child's writing skills as well as the child's interest in writing.

Numeracy

Teacher rating of numeracy skills: teacher yes/no ratings on five items; 0 (poor skills) to 5 (strong skills); available on about 64 per cent of sample. Items assess the child's ability to perform numeric tasks such as counting, classifying, and simple addition, along with the ability to recognise numbers.

Approach to learning

Who Am I? (WAI): standardised score based on interviewer administration of the Who Am I? (ACER 1999), an Australian measure which assesses a child's ability to perform a range of tasks such as reading, writing, copying, and symbol recognition as a measure of school readiness.