Returns of Parent and Twin Web Data
Parent and twin data were collected exclusively by means of web activities. Although many parents initially gave written consent, by returning the consent postcard, this was not a requirement in order for families to be invited to do the web activities. This was because the web activities started with an on line consent form, which had to be completed before families could proceed with the activities.
The invitations to complete the web activities, and the necessary login details, were sent by mail. The mailing was followed up by telephone calls from the web callers.
The data from the web activities were collected automatically by programs on the web server. There was no loss of data in this process, so the returns of data shown in the table below also represent actual data in the analysis dataset.
The figures shown in the table below are numbers of families (twin pairs).
| School cohort | 1 | 2 | TOTAL |
|---|---|---|---|
| Twin birth dates | Jan-94 to Aug-94 | Sep-94 to Aug-95 | |
| Original TEDS sample | 3265 | 4888 | 8153 |
| Families contacted (mailed initial consent details and/or mailed login details and/or called by telephone) | 1597 | 4346 | 5943 |
| On line consent form completed | 1145 | 2250 | 3395 |
| Percentage of contacted families giving on line consent | 71.7% | 51.8% | 57.1% |
| Parent web questionnaires completed | 1089 | 2095 | 3184 |
| Percentage of contacted families that completed the parent questionnaire | 68.2% | 48.2% | 53.6% |
| Complete twin web data (all web tests completed by both twins) | 833 | 1802 | 2635 |
| Percentage of contacted families that returned complete twin web data | 52.2% | 41.5% | 44.3% |
| Partial twin web data (at least one web test completed by at least one twin) | 252 | 352 | 604 |
| Percentage of contacted families that returned any twin web data (partial or complete) | 67.9% | 49.6% | 54.5% |
Returns of Teacher Questionnaire Data
Teacher data were collected by means of paper questionnaires. Prior to sending the questionnaires, parents were asked for specific consent to contact the twins' teachers, and for the teachers' contact details. This information was initially collected by mail, using the consent postcards, and subsequently by telephone, by web callers.
For most families, both twins were taught by the same teacher. However, for some families the two twins were taught by different teachers, and this resulted in some returns of unpaired data.
Most of the figures in the table below are based on information logged in the TEDS admin database. However, figures for 'data in the dataset' are based on the final analysis dataset itself. Discrepancies between returns and actual data arise because of logging errors, unusable data, and losses of data.
The figures shown in the table below are numbers of families (twin pairs).
| School cohort | 1 | 2 | TOTAL |
|---|---|---|---|
| Twin birth dates | Jan-94 to Aug-94 | Sep-94 to Aug-95 | |
| Original TEDS sample | 3265 | 4888 | 8153 |
| Consents sent | 1589 | 4260 | 5849 |
| Parents gave consent to contact teachers | 1372 | 2520 | 3892 |
| Percentage of contacted families giving teacher consent | 86.3% | 59.2% | 66.5% |
| Teacher booklets sent (pairs) | 1368 | 2519 | 3887 |
| Teacher booklets returned for both twins | 960 | 1939 | 2899 |
| Teacher booklets returned for only one twin | 113 | 259 | 372 |
| Percentage of booklets sent that were returned: | 74.3% | 82.1% | 79.4% |
| Paired data in the dataset | 956 | 1933 | 2889 |
| Unpaired data in the dataset | 116 | 266 | 382 |