TEDS Data Dictionary

Description of Test

This test was a significantly changed version of the Vocabulary test that was used in the 12 Year study. For this 14 Year version, the first three of the 12 Year items were removed, and the remaining 27 items were re-ordered (in an attempt to achieve a more consistently increasing difficulty gradient). Furthermore, the branching was entirely removed, and the discontinue rule was modified.

The test consisted of a series of vocabulary questions. For each question, there were either three or four possible responses; the twin selected a response by clicking on it on the screen. There were 27 items: the questions and responses are tabulated below. The items were presented to each twin in ascending numerical order, without branching. A twin taking the test may have been presented with fewer than 27 items, because of the discontinue rule (see test rules below).

Each item was presented in two ways: as text on the screen, and as an audio recording. The text and audio file for each item were downloaded immediately before the item was presented. The audio recording was included as an aid to any twins with reading difficulties; this test was not intended to assess reading ability in addition to vocabulary knowledge. The text of each item, together with the responses, are shown in full in the table of test items at the bottom of this page.

Test Rules

• Scoring
  For questions 1, 2, 6, 9 and 10, the correct response is given a score of 2, and any of the two or three incorrect responses is given a score of 0 (questions 2 and 10 each have three possible responses; all other questions have four possible responses).
  For all questions other than 1, 2, 6, 9 and 10, there are two correct responses; the best response is given a score of 2, and the second-best response is given a score of 1. Each of the other two (incorrect) responses is given a score of 0.
  The maximum total score for the test is 54.
• Ordering of items
  Items are presented in ascending order of item number, subject to the discontinue rule below. There are no branching rules.
• Discontinue rule
  Discontinue the test after five scores of zero in any five consecutive items. This rule applies throughout the test, from item 1 onwards.
• Timeout rule
  There is no special timeout rule for this test, so the default timeout of 5 minutes applies to each item. In practice, it was found that item timeouts did not occur in this test.

Item Variables

The item variables relating to the Vocabulary test, as listed in the table below, were generated automatically by programs on the web server during the course of the test. Note that the dataset only includes data for completed tests. If a twin started the test but left it unfinished, then the data for the test were not used. Note that the variable holding the total test score was also generated automatically on the web server. It is therefore treated as an item variable (it did not have to be derived as at age 10).

In most cases the values of these variables have been left unaltered, although some have been recoded during data cleaning as follows. See the web data cleaning page for further details.

• For items skipped due to the discontinue rule, the item response variable is recoded from missing to -2, and the item score is recoded from missing to 0.
• For items that were interrupted, crashed or malfunctioned in any way, the item response variable is recoded from missing to -4, and the item score is recoded from missing to 0.
• For instances of tests compromised by excessive loss of data, the status flag is recoded from 2 to 3, the data flag is recoded from 1 to 0, and all item variables are recoded to missing (test data deleted)
• For twins identified as random responders in this test, the status flag is recoded from 2 to 4, the data flag is recoded from 1 to 0, and all item variables are recoded to missing (test data deleted)

The test start and end dates and times, and item answer and download times, have not been retained in the dataset.

Test Items

The numbering of the items, shown in the table below, equates to the numbering used in the item variables. This is the same as the order in which items were presented to twins in the test, subject to the discontinue rule (see test rules above).