Data collection periods were linked to the school year (September to August) in which twins reached the age of 10 years. The reason for this was to ensure that all twins were in the same school year when the teacher data were collected. Hence, families were divided into school cohorts according to when their twins were born (as described above). This simplified administration of the study, because all families in a cohort could be contacted at once. Twin ages varied from roughly nine and a half to ten and a half years, at the time when the data were collected.
For families not known to have address problems, initial contact was made by sending them an information pack together with a consent form (pdf); the latter was printed on a postage-paid postcard. In the consent form, parents were asked to consent to (or opt out of) the web study; and they were also asked for consent to contact the twins' teachers (they were also asked to provide teacher/school contact details). Up to two written reminders were sent to families that did not return the consent forms promptly.
Every family that had not explicitly opted out of the study was later sent a login pack. This pack contained the family's login details (username and password) for the web activities, and a guidance sheet (pdf). The latter contained basic instructions for accessing the web tests.
All families that had been sent a login pack, plus families with address problems that had not been contacted by mail, were subsequently contacted by telephone. This was done by "web callers", staff employed by TEDS to contact the families involved in the web study, in order to encourage them to complete the web activities and to help them with problems. Full details of the web tests, including a description of the role of the web callers, are on a separate page.
On completion of the web tests, each twin was rewarded with vouchers (to the value of £5 for each twin). A further £5 voucher was included for the parents, as a way of covering their internet connection costs.
The progress of each family in their web activities was recorded on the web server. For administrative purposes (for example, in order to allocate families to web callers, and in order to organize mailings of vouchers), information had to be transferred from the web server to the TEDS administrative database. This was done by means of a "family status file", which was produced automatically every night by a program running on the web server. The analysis file was a plain text file (in csv format), with a row of data for every family. The information recorded for each family included fields to show whether each twin had started or finished each of the web tests, together with dates, times, and other information.
The teacher study included all families that had given consent and provided contact details for the twins' teachers and schools. Families may have done this in writing via the consent form, or verbally via the web callers. Teacher questionnaires (pdf) were sent directly to teachers, and were not seen by the families themselves. Up to three written reminders were sent to teachers that had not returned their questionnaires promptly. A telephone reminder was also used for teachers in some prioritized cases.
The measures used in the web activities and teacher questionnaires are described in detail on another page.
General data entry issues (for all studies) are described in a separate page. In the 10 Year study, data from the web activities were effectively entered by the parents and twins themselves. As they answered items on their computers, their responses were recorded on the TEDS web server.
The web server was programmed to produce, when required, "analysis files" containing the web test data. There was a specific analysis file for each web activity. Each analysis file is a plain text file, with comma-delimited variables, containing one row of data for each twin who completed the test. The analysis files were copied from the web server when they were needed for construction of the dataset. The data files are described in detail in another page.
The teacher questionnaires were entered by means of optical scanning. The layout of the questionnaires had been designed with this in mind. The scanning was handled externally by Group Sigma, a commercial company. The questionnaires were returned by mail from teachers to the TEDS office. They were then delivered to Group Sigma in batches for scanning. After scanning each batch of booklets, Group Sigma returned the data in plain text files (the data files are described in detail in another page).
The annotated version of the teacher questionnaire (pdf) shows, in green, the scan positions used for each field in the Group Sigma raw data files. It also shows, in blue, the field names and value codes that have been used in the cleaned raw data.
The files of raw scanned data, as returned by Group Sigma, have been retained for reference. After data cleaning, the teacher data were aggregated and stored in a single Access database file. This Access database is now treated as the master copy or source of all 10 Year teacher data to be used in analysis. Note however that the raw web data (in analysis files) is stored separately, partly because of the large size of these files. All the raw data files are described in full in 10 Year raw data files.