TEDS Data Dictionary

1st Contact 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 returns and actual data arise because of logging errors, unusable data, and losses of data.

The numbers of families contacted, and the numbers of booklets returned, are totals from all waves of 1st Contact data collection. This therefore includes not just the initial mailings between 1995 and 1998, but also the later waves in 2000-01, 2004-06 and 2013.

Note that, at the time of this study, attempts were made to collect data from all apparently contactable families in the original ONS sample. This included inactive families (never returned data and never enrolled) who were later removed from the TEDS sample, as explained on the main 1st Contact page. All parents who returned the 1st Contact booklets were active and therefore have remained part of the TEDS sample.

The first table below shows the numbers contacted in the original ONS family. This table therefore illustrates both the raw data returns, and the success rate in enrolling families into the TEDS sample via the 1st Contact study.

The second table is provided for comparability with later studies: it shows the numbers contacted who have remained in the TEDS sample after removal of inactive families in 2004.

The figures shown in both tables below are numbers of families (twin pairs).

ONS Sample

This table illustrates actual returns from families who were contacted in the original ONS sample.

Cohort (birth year of twins):	1994	1995	1996	TOTAL
Original ONS sample:	5640	5710	5460	16810
1st Contact booklets sent (at any time)	5405	5537	5358	16300
1st Contact booklets returned in the original mailing, 1995-98	4759	4688	3845	13292
Percentage of booklets returned in the original mailing, 1995-98	88.0%	84.7%	71.8%	81.5%
1st Contact data returned after 1999 *	79	124	246	449
Total 1st Contact booklets returned	4838	4812	4081	13741
Overall percentage returns for booklets sent in the ONS sample	89.5%	86.9%	76.4%	84.3%
Data in the dataset	4835	4801	4081	13717

* includes the 'You and Your Family' booklets sent in 2000-01, data collected by phone in 2004-06, and shortened booklets sent in 2013.

TEDS Sample

This table illustrates the proportion of families in the TEDS sample who have returned 1st Contact data.

The small numbers of families that are in the TEDS sample but that have not returned 1st Contact data are those who effectively enrolled in TEDS at a later date, through participation in other TEDS studies.

Cohort (birth year of twins):	1994	1995	1996	TOTAL
TEDS sample:	4912	4901	4132	13945
1st Contact booklets sent to families in the TEDS sample	4907	4900	4129	13936
Total 1st Contact booklets returned by families in the TEDS sample	4842	4806	4088	13736
% of families in the TEDS sample who have returned 1st Contact data	98.7%	98.1%	99.0%	98.6%