TEDS Data Dictionary

12 Year Data Returns

Most of the figures in the tables 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 apparent returns and actual data arise because of logging errors, unusable data, and losses of data.

The main 12 Year Study page gives full details of how the data were collected. Note that there are some significant differences in data returns between the cohorts, sometimes as a result of changes in data collection procedures, and sometimes as a result of differences in twin age (some twins were in primary school and some in secondary school when the data were collected).

Contents of this page:

Returns of Family Questionnaire Data

The figures shown in the table below are numbers of families (twin pairs).

School cohort 1 2 3 & 4 TOTAL
Twin birth dates Jan-94 to Aug-94 Sep-94 to Aug-95 Sep-95 to Dec-96
Original TEDS sample 3265 4888 5792 13945
Questionnaire + consent pack sent 2189 2697 3553 8439
Consent given (written or verbal) 1304 1857 2420 5581
Percentage of consent returns 59.6% 68.9% 68.1% 66.1%
Booklets returned (all three) 1383 1954 2520 5857
Percentage of families returning all three booklets 63.2% 72.5% 70.9% 69.4%
Partial returns (one or two booklets) 21 19 25 65
NC attainment questionnaires sent 1064 1853 2465 5382
NC attainment questionnaires back 700 1080 263 2043
Percentage of NC attainment questionnaires back 65.8% 58.3% 10.7% 40.0%
Parent booklet data in the dataset 1392 1961 2523 5876
Paired twin booklet data in the dataset 1389 1950 2522 5858
Unpaired twin booklet data in the dataset 8 12 11 31
Parent NC data in the dataset 700 1078 262 2040

Returns of Twin Web and TOWRE Data

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 3 & 4 TOTAL
Twin birth dates Jan-94 to Aug-94 Sep-94 to Aug-95 Sep-95 to Dec-96
Original TEDS sample 3265 4888 5792 13945
Families sent web login details 2112 2640 3485 8237
On line consent form completed 1384 1954 2561 5899
Percentage of contacted families giving on line consent 65.5% 74.0% 73.5% 71.6%
All web tests completed (both batteries, both twins) 572 1459 1948 3979
Twins only completed the 1st battery of web tests 555 56 55 666
Some web tests completed (but both twins did not finish the first battery) 234 533 705 1472
Percentage of contacted families with ALL web tests completed 27.1% 55.3% 55.9% 48.3%
Percentage of contacted families with ANY twin web data (partial or complete) 64.4% 77.6% 77.7% 74.3%
Attempted contact for TOWRE telephone tests 2062 1459 1949 5475
TOWRE tests completed (both twins) 1401 1381 1871 4647
Percentage of contacted families with TOWRE tests completed 67.9% 94.7% 96.0% 84.9%

Returns of Teacher Questionnaire Data

The figures shown in the table below are numbers of families (twin pairs).

School cohort 1 2 3 & 4 TOTAL
Twin birth dates Jan-94 to Aug-94 Sep-94 to Aug-95 Sep-95 to Dec-96
Original TEDS sample 3265 4888 5792 13945
Consents sent 2189 2697 3553 8439
Parents gave consent (written or verbal) to contact teachers 1642 1849 2877 6368
Percentage of contacted families giving teacher consent 75.0% 68.6% 81.0% 75.5%
Teacher questionnaires sent (pairs) 1630 1844 2867 6341
Teacher questionnaires returned for both twins 965 1083 2358 4406
Teacher questionnaires returned for only one twin 407 485 203 1095
Percentage of questionnaires sent that were returned: 71.7% 71.9% 85.8% 78.1%
Paired data in the dataset 955 1078 2351 4384
Unpaired data in the dataset 414 489 209 1112