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Frequently Asked Questions

Supplemental Data

What supplemental data are available?

The ECLS B currently has two supplemental datasets associated with it: the Twin Triad dataset and the Reading Aloud Profile – Together (RAPT) dataset.

The Twin Triad file consists of data from the 9-month collection for more than 50 twin pairs. The supplemental Twin Triad study is a modification of the 9-month teaching activity (The Nursing Child Assessment Teaching Scale, or NCATS). In the regular NCATS activity protocol, the parent was asked to interact with his/her child one-on-one and to teach the child one of a selected set of tasks that was slightly beyond the child’s current abilities (e.g., how to stack a set of blocks). All the twins in the sample completed the NCATS task individually with their caregiver (usually the mother). However, a subset of twin pairs and their mothers agreed to do the NCATS task a third time, in a triadic interaction such that the mother simultaneously attempted to teach both twins a new NCATS task (one not yet attempted). The Twin Triad file contains information on how the threesome interacted during the teaching task and thus sheds light on how the triad might interact naturally in their day-to-day lives (as triadic interactions may be more common for twins than the one-on-one interactions observed in the dyadic NCATS interaction). The Twin Triad dataset is a supplemental restricted-use dataset and is available to restricted-use license holders upon request to the IES Data Security Office (

The Reading Aloud Profile – Together (RAPT) data provide detailed information about parents’ and children’s behaviors while engaged in the joint book reading activity of the preschool Two Bags Task. In the preschool Two Bags Task the parent and child were given 10 minutes to play with the contents of two bags. The first bag contained a book to read and the second bag contained toys with which to play. The RAPT data can be used to examine whether joint book reading behaviors of parents and children vary by family and child characteristics and whether joint book reading behaviors relate to children’s early reading competency at preschool and upon entry to kindergarten. The RAPT sample of approximately 800 cases is a random sample drawn from the larger ECLS-B sample, so all the oversamples are represented, though it may not be able possible to study each oversample group individually using the RAPT data due to relatively small subgroup sample sizes. Although the RAPT data were initially released as a separate dataset, they are now included in the longitudinal 9-month—kindergarten 2007 restricted-use data file. For more information on the RAPT, see the Early Childhood Longitudinal Study, Birth Cohort (ECLSB), Preschool–Kindergarten 2007 Psychometric Report (NCES 2010-009) (Najarian et al. 2010).

How do I determine if a case is in one of the supplemental samples?

In order to determine which twins are included in the Twin Triad dataset, one must request the Twin Triad dataset and merge it to the main data file using child ID. In order to determine if a case was included in the RAPT study, one may use any one of the Z3 variables. If a case has valid data for a Z3 variable, then it was included in the RAPT sample.

Can you apply the weights to the supplemental samples to get national estimates?

You cannot apply weights to the Twin Triad sample to obtain national estimates because the sample was not a random sample. Consequently, the findings can only be generalized to twins with caution. The RAPT sample, however, is a random sample of study children with Two Bags Task data. RAPT data can be weighted using a main sample weight adjusted by multiplying by the inverse of the probability of selection (for example, W3R0 * [8,900/800]).