APPENDIX 1: FURTHER DETAILS OF EXPLANATORY AND OUTCOME VARIABLES
Social background variables
Equivalised annual household income
The income that a household needs to attain a given standard of living will depend on its size and composition. For example, a couple with dependent children will need a higher income than a single person with no children to attain the same material living standards. 'Equivalisation' means adjusting a household's income for size and composition so that we can look at the incomes of all households on a comparable basis.
Socio-economic classification ( NS- SEC)
The National Statistics Socio-economic Classification ( NS- SEC) is a social classification system that attempts to classify groups on the basis of employment relations, based on characteristics such as career prospects, autonomy, mode of payment and period of notice. There are fourteen operational categories representing different groups of occupations (for example higher and lower managerial, higher and lower professional) and a further three 'residual' categories for full-time students, occupations that cannot be classified due to a lack of information or other reasons. The operational categories may be collapsed to form a nine-, eight-, five- or three-category system.
This report uses a five-category system in which respondents and their partner, where applicable, are classified as managerial and professional, intermediate, small employers and own account workers, lower supervisory and technical, and semi-routine and routine occupations. The variable is measured at household level. In couple families this corresponds to the highest classification amongst the respondent and his/her partner.
Parental level of education
At the first wave of data collection, each parent was asked to provide information on the nature and level of any school and post-school qualifications they had obtained. The information is updated at each subsequent contact. Qualifications are grouped according to their equivalent position on the Scottish Credit and Qualifications Framework which ranges from Access 1 to Doctorate. These are further banded to create the following categories: Degree-level academic or vocational qualifications, Higher Grades or equivalent vocational qualification ( e.g. SVQ 3), Upper-level Standard Grades (grades 1 to 4) or equivalent vocational qualification ( e.g. SVQ 1 or 2), Lower-level Standard grades (grades 5 to 7) or equivalent vocational qualifications ( e.g. Access 1 or 2, National Certificates). The highest qualification is defined for each parent and a household level variable is calculated. In In couple families this corresponds to the highest classification amongst the respondent and his/her partner.
Family type transitions
Using information on family type (couple family or lone parent household) collected at every sweep, a variable was constructed which measured stability or changes in family type between the ages of 10 months and 3 years (sweeps 1 to 3). Four classifications were derived: stable couple family, couple who separate, stable lone parent and lone parent who repartnered.
Home learning environment
The index of the children's home learning environment was originally developed to assess the association between children's activities at 22 and 34 months and their cognitive development at 34 months (Melhuish, 2010). The index covers aspects such as: how often the children have been read to; done activities such as painting, singing rhymes, or playing educational games; and the number of books in the home. Higher scores on the index indicate children who have experienced a higher number of these items.
Rules and routines
Rules and routines were measured at sweeps 2 and 5. A count of the number of 'rules' or routines was derived from the following: 'always' responses to question on regular meals at sweep 2, a question on regular bedtime at sweep 5 and four questions at sweep 5 on whether the child had to tidy up toys, brush teeth, stay in room, and turn off TV or music in room (using 4-point scale - always/usually/sometimes/never or almost never). The number of rules was banded into low (0-3 rules), medium (4-5 rules) or high (all 6 rules).
At age 2 (22 months, sweep 2) and age 4 (46 months, sweep 4), parents were asked the extent to which they had ever used a range of discipline approaches with the cohort child. The approaches included were:
- Time out
- Reward system/sticker chart
- Ignoring bad behaviour
- Naughty step/room/corner
- Raising your voice or shouting
- Removing treats or privileges
Responses to the items on smacking were combined to create a single variable indicating whether smacking had ever been used.
Early mother-infant attachment was measured at sweep 1 using an abbreviated six-item version of the Condon mother-infant attachment scale (Condon and Corkindale 1998). Mothers were asked about their feelings for their child, with four different possible responses for each item. Items in the scale had low reliability 31 (Cronbach alpha=0.52), but the measure was retained in this study because of the likely policy interest in associations between early indicators of the mother-child relationship and health. The scale used in this report was created by taking the responses to four of the six items - those answers which showed an absence of feelings of annoyance and resentment and feeling patient and confident all the time or most of the time. Each response was divided into positive and negative categories. The revised scale counted the number of responses in the 'positive' category. A score of four, that is a positive relation to the child on all four items, was taken as showing good maternal attachment.
Parent's problems with reading or writing
At sweep 4, respondents were asked two questions designed to measure difficulties with reading and writing. At each question respondent's were asked to indicate whether they had any difficulties with specific tasks. For example, in relation to reading these included understanding what is written in a newspaper and reading aloud from a children's storybook, for writing they included spelling words correctly and making handwriting easy to read. Responses across all items were combined into a single binary variable indicating whether the respondent mentioned any difficulty with reading or writing.
Experience of formal childcare before age 3
Information on use of regular non-parental care collected in GUS includes whether that care is provided through a formal or informal setting. Formal providers include private, workplace and local authority nurseries, childminders and playgroups. Data from sweeps 1 to 3 was combined to generate a binary variable indicating whether or not the child had been cared for on a regular basis by any of these formal providers at any time between the ages of 10 months and 34 months.
Pre-school education is delivered through a range of settings. Respondents were asked to indicate which type of setting the child was attending for pre-school education or if the child was not attending pre-school. A choice of nine pre-school settings was available. These responses were collapsed to represent five main categories: no pre-school, nursery class attached to an independent or local authority primary school, local authority nursery school, private day nursery or nursery school, or another type of provider. Note that private day nurseries or nursery schools include only commercially operating daycare providers rather than independent schools (which are captured via the nursery class attached to a primary school category).
Perceived readiness for pre-school
A series of six items were included at sweep 4 in order to measure the respondent's perception of the child's 'readiness' for pre-school. These items took the form of statements suggesting various skills or behaviours considered necessary for a comfortable transition into the pre-school environment. They included issues with separation from parent, child's reluctance to attend, ability to mix with other children, ability to take turns and share, whether the child was sufficiently toilet trained, and whether the child was independent enough to cope. Respondents were asked the extent to which they agreed or disagreed on each scale. Responses were then summed into a scale with a higher score indicating a perceived higher readiness. Children were then classified into one of two groups according to whether they had an average or above average score, or a below average score on the scale.
Duration of pre-school attended prior to assessment
This is calculated as the number of months between the date the child started pre-school and the date at which their cognitive assessment was administered during the sweep 5 fieldwork. The figure does not allow for school holidays or child absences so is not a precise measure of the duration of pre-school which the child has experienced, however it is considered to provide a proxy for that information.
Children's general health
At each sweep of fieldwork, parents are asked to rate their child's general health on a five-point scale ranging from very good through to very bad. The measure used in this report captures changes in child's health status between the ages of 10 and 34 months (sweeps 1 to 3). Children who were reported to have fair, bad or very bad health at any or all time points were categorised as temporarily or always having fair, bad or very bad health.
Low birth weight
Any child with a birth weight of less than 2500 grammes at full term was classified as having a low birth weight. The measure includes full-term (born at or after 37 weeks gestation) babies only.
Infant/toddler checklist of the Communication and Symbolic Behaviour Scales
The Infant/Toddler checklist of the Communication and Symbolic Behaviour ( CSBS) (Wetherby and Prizant, 2001) assesses children's communicative development at 6-24 months. This instrument was included in the self-completion section of the sweep 3 survey when the cohort children were aged 22 months (just under 2 years old). Three principle domains are assessed in the checklist - social communication, expressive speech/language and symbolic functioning - with a composite score provided for each element. A total score can also be calculated by summing the three composite scores. This report uses the total score. A higher score indicates better communicative development and language skills.
Level of physical activity
Data from questions on sedentary and physical activities asked at sweep 3, when the child was aged 3 (34 months) were used to form a combined physical activity score. More specifically, the questions used were:
- The number of days the child had played outside in the previous week
- The number of days the child had played on the computer in the previous week
- The number of hours of TV the child watched on the average weekday
- The amount of time in the previous week spent: riding a bike, throwing or kicking a ball, dancing or gymnastics, running and/or jumping, playing on a trampoline, swimming, playing at a soft play area or ball swamp, playing at a swing/play park, or doing another physical activity
The scale had a range of 0 to 66, with 0 being no physical activity and a large amount of sedentary activity, and 66 being the reverse. The scale was banded to create three similarly sized groups indicating low, medium and high levels of activity.
To explore variations in social networks three summary indicators were created using data collected at sweeps 2 and 3 - one focused on satisfactory friendship networks, one focused on satisfactory family networks and the final one identified those people who had neither a satisfactory friendship nor family network.
Respondents were considered to have a satisfactory friendship network if they agreed with the statement "My friends take notice of my opinions", and they reported one of the following: visited by friends with children once a fortnight or more often; visits friends with children once a fortnight or more often; attends a parent and toddler group; uses friends for childcare support in the first instance. Respondents were considered to have a satisfactory family network if they agreed with the statement: "I feel close to my family" and they reported any one of the following: any set of the child's grandparents see the child at least once a week; uses a relative for childcare support in the first instance.
At sweeps 1 to 3, respondents were asked whether they had attended any parenting classes or groups "where parents have the chance to improve their parenting skills and knowledge". Responses across the three sweeps were combined to create a single binary variable indicating any attendance at such at parenting classes over that period.
Maternal mental health
GUS has measured maternal mental health using two different scales: at sweeps 1 and 3 (ages 10 months and 34 months respectively), the SF12 Mental Health Component Score ( MCS) was used, whereas at sweeps 2 and 4 (ages 22 months and 46 months respectively) selected items from the Depression, Anxiety and Stress Scale ( DASS10) were used. 11 Both scales are widely used and well validated.
In this report, a respondent is defined as having 'poor' mental health if she has a score on SF12 ( MCS) at sweep 1 or sweep 3 which fell more than one standard deviation below the mean population score for that sweep. A binary variable was created to indicate if the poor maternal mental health was reported at either sweep 1 or sweep 3.
Maternal general health
General health is measured at every sweep by asking respondents to indicate whether they think their health is excellent, very good, good, fair or poor. Responses from sweeps 1 to 3 were combined into a single binary variable which indicated whether the respondent had reported 'fair' or 'poor' health at any of those contacts.
This measure is used to provide an alternative, direct, assessment of family deprivation to that offered by indirect income-based measures. Items assessing material deprivation were first developed for use in the Family Resources Survey in 2004/05 and now form part of UK government's measure of child poverty. The data used in this report was collected at sweep 4 and consists of a series of 21 questions assessing the extent to which the family are unable to afford various household, child or adult goods or unable to participate in various activities due to lack of money. The index measure used here counts the number of items where the respondent indicates that they 'cannot afford this at the moment'. A weight is then applied to those items that more people have. A higher score indicates a higher level of material deprivation.
Area deprivation ( SIMD)
Area deprivation is measured using the Scottish Index of Multiple Deprivation ( SIMD) which identifies small area concentrations of multiple deprivation across Scotland. It is based on 37 indicators in the seven individual domains of Current Income, Employment, Health, Education Skills and Training, Geographic Access to Services (including public transport travel times for the first time), Housing and a new Crime Domain. SIMD is presented at data zone level, enabling small pockets of deprivation to be identified. The data zones, which have a median population size of 769, are ranked from most deprived (1) to least deprived (6,505) on the overall SIMD and on each of the individual domains. The result is a comprehensive picture of relative area deprivation across Scotland.
In this report, the data zones are grouped into quintiles. Quintiles are percentiles which divide a distribution into fifths, i.e., the 20th, 40th, 60th, and 80th percentiles. Those respondents whose postcode falls into the first quintile are said to live in one of the 20% least deprived areas in Scotland. Those whose postcode falls into the fifth quintile are said to live in one of the 20% most deprived areas in Scotland.
Further details on SIMD can be found on the Scottish Government website http://www.scotland.gov.uk/Topics/Statistics/SIMD/Overview (Footnotes)