TEDS Data Dictionary

4 Year Study

Contents of this page:

Introduction

The 4 Year study data were collected by means of booklets:

  • Parent booklets.
    Parent-reported data, relating mainly to the family (but with some twin-specific items).
  • Twin booklets.
    Parent-reported data specific to each twin, including various language and behaviour measures. Included the "Parca" parent-administered cognitive tests.

The measures used in the booklets are described in full in a separate page.

The 4 Year data were collected between 1998 and 2000 from all TEDS families (twins born between 1994 and 1996). Data collection was timed to coincide as closely as possible with the twins' 4th birthdays.

The sample

The 4 Year sample included all three birth cohorts (1994, 1995 and 1996). Families were generally excluded from the 4 Year sample if they had not returned the 1st Contact booklet. In addition, in the 1994 cohort only, families were excluded from the 4 Year sample if they had returned neither the 3 year nor the 2 year booklets. However, there were exceptions to these rules.

The 4 Year booklets were sent to roughly 12500 of the 16810 families in the original TEDS sample from ONS. Hence there were around 4300 families that were not sent the 4 Year booklets. Roughly 2000 of these had withdrawn from TEDS or were known address problems; the remainder were mostly families that had not returned the 1st Contact booklet, or families in the 1994 cohort that had returned neither the 2 year nor the 3 year booklets.

The data returns for the 4 Year study are summarised in a separate page. There are further pages comparing samples and returns for different TEDS studies.

Data collection

Each family in the sample was sent three booklets: a parent booklet plus two copies of the child booklet (pdfs). The parent booklet included a consent form on the first page. The measures used in the booklets are described in detail on another page. The measures were entirely parent-reported, although the child booklet included cognitive tests that were administered by the parents on the children.

The booklets were designed to be completed when the twins were precisely 4 years old; they were therefore sent to families at or just before the twins' 4th birthdays. This involved regular mailings of booklets (generally once per month) between December 1997 and December 2000.

Regular reminders were sent to families who did not return the booklets promptly. Up to 8 reminders were sent, over a period of up to 11 months after the original booklets were sent to each family.

Data entry

General data entry issues are described in another page. In the 4 Year study, data entry was handled externally by NOP Numbers, a commercial company. The data were originally returned in pre-formatted Excel workbooks containing multiple worksheets. It is not clear whether the data were entered directly into Excel, or whether the data were exported into Excel after data entry into some other software system.

Data entry staff at NOP carried out basic coding of the raw data by converting tick boxes to numeric code values - the raw data item coding is shown in the annotated parent and child booklets (pdfs). The Drawing task items in the child booklet were scored by TEDS staff before the booklets were sent to NOP. The Drawing items (with the exception of the new "Draw a Man" task) were the same at age 4 as at age 3; the coding rules for these items are fully described in 3 Year Drawing coding (pdf).

The inside front cover of the 4 Year parent booklet asked for contact details of a relative or friend of the family; and the first page of the booklet is a consent form, asking for family name and address details. New sibling details were also collected on page 1. The verbatim text data from these sections were entered into the TEDS admin system at the time of data collection, but have not been retained within the raw data files.

In the main body of the booklets (notably the parent booklet) there were some items where a free text response was invited. However, the verbatim text data were recorded for a few of these items at the time of data entry. For these few items, the original, raw verbatim text responses were coded into numeric categories, so that they could be used in dataset variables. The original text responses (whether originally entered or not) have not been retained in the cleaned raw data. The parent booklet coding (pdf) shows the positions of text items and which items were entered then coded.

The original raw data files were cleaned and aggregated together, and stored in a single Access database files (see 4 Year raw data files for details). This Access database is now the master copy of all 4 Year data for construction of the dataset. The ways in which the raw data have been cleaned are described in another page.