TEDS Data Dictionary

Description of Test

This test of language ability consisted of a series of items in which twins had to select two sentences with similar (or identical) meanings, from three sentences played using audio recordings. There was a practice item followed by 35 main items (the practice item contributed to the branching, but not to the overall score). The items, together with the responses and correct answers, and shown in detail in the table of test items below.

In each item, three sentences (labelled A,B,C) were played using audio recordings; after each sentence, the letter A, B or C respectively was highlighted on the screen. Note, however, that the text of the sentences was not displayed on screen. Twins were able to click a "listen again" button to hear the three sentences again if they wished. The tutorial, played before the test starts, was used to establish whether the computer's sound is turned on, in order to discourage twins from attempting the test without sound.

To respond to each item, twins were asked to click on the two letters (A/B/C) for the two sentences having the same meaning; and then to click on "OK". The test was programmed to prevent twins from proceeding if they had selected 0, 1 or 3 letters. Each item had a time limit of 45 seconds in which a twin had to answer.

The test had complex branching and discontinue rules (see test rules below). Because of these rules, any given twin taking the test may have been presented with fewer than 35 of the main items, and the order in which the items are presented was highly variable.

Test Rules

• Answering items
  Items are presented in the order defined by the branching/discontinue rules, explained below. For each item, the twin is required to select two of the three responses (A,B,C) by clicking on them, then to click on "OK". If a twin attempts to select all three responses, or if a twin attempts to click on "OK" (within the item time limit) after selecting fewer than two responses, then they are not allowed to continue; instead, a message appears, reminding them what they should do.
• Timing rule
  There is a time limit of 45 seconds for answering each item. Timing starts after the 3 audio sentences have been played (timing continues even if the twin clicks "Listen Again" to replay the sentences).
  If 45 seconds expires before the twin has clicked on "OK", any responses (A, B or C) selected by the twin are automatically submitted, and may receive a correct or incorrect score; if no responses have been selected, then the item is forfeited with zero score. The item is removed from the screen to be replaced by a link to the next item (so the twin can continue with the test).
• Definitions
  The branching/discontinue rules are complex, and are based on the following definitions (which are specific to this test).
  • Basal:
    A sequence of 5 correctly-answered, consecutively-numbered items. The basal can occur anywhere in the test. The 5 items need not necessarily be attempted consecutively, because of branching (for example, they could include items 10,11,12 followed later by items 9 and 8). It is possible for two or more such sequences to occur in a test; if so, then the highest-numbered such sequence is defined as the basal (for example, if items 11-15 and items 20-24 are all correct, then the basal occurs at items 20-24). It is also possible that no such sequence of 5 items occurs during a test; if so, then by default item 1 is defined as the basal point.
  • Ceiling:
    A sequence of 5 or fewer consecutive items that include 3 incorrectly-answered items. The 5 items must be both consecutively-numbered and consecutively-answered; they may not include items 6,7,8,9 if these are attempted in reverse order (see branching rules below); however, there are no other restrictions on where a ceiling may occur. (For example, the ceiling may include items 6,7,8,9 if attempted in ascending order; and a ceiling may occur at items 1,2,3,4,5 when attempted in reverse order.) It is possible for two such sequences to occur during a test: one above item 10, followed later (after branching) by another in items 1-5; if so, then the ceiling is defined as items 1-5. It is also possible that no such sequence occurs during a test; if so, then by default item 35 is defined as the ceiling.
• Branching and Discontinue rules
  
  • Start with the practice item, P1.
  • If the practice item P1 is answered incorrectly, go to item 1. Then attempt items in ascending order (1,2,3...) until a ceiling is reached, then discontinue the test. If no ceiling is reached, continue right through to item 35 (the default ceiling), then discontinue the test.
  • If the practice item P1 is answered correctly, go to item 10. Then attempt items in ascending order (10,11,12...) until a ceiling is reached (if no ceiling is reached, continue right through to the default ceiling of item 35). Then:
    • If a basal has been attained (between item 10 and the ceiling), then discontinue the test.
    • If no basal has yet been attained, other than the default basal of item 1, branch down to item 9 and continue with items in reverse order (9,8,7...), until a basal is attained; then discontinue the test. If no basal is attained, continue right down to item 1 (the default basal), then discontinue the test. Note that this may result in the formation of a new ceiling in items 1-5.
• Scoring
  
  • Scoring applies to items 1 to 35, but not to the practice item P1.
    For each item, the correct pair of sentences is given a score of 1; all other responses are incorrect, and are given a score of 0.
  • If and when a basal has been attained, every item below the basal is credited with a score of 1, as if it had been answered correctly. Note that, as a result, some items already attempted and answered incorrectly can later be credited with a score of 1.
    If no basal is attained, so that item 1 is used as the default basal, then no crediting takes place.
  • Items above the ceiling are not counted towards the total score.
    Normally, the test discontinues when a ceiling is reached, so items above the ceiling are not attempted. However, as explained above, it is possible to reach a ceiling somewhere above item 10, and then to establish a new ceiling while attempting items 1-5 (in reverse order); in these circumstances, some items originally answered correctly (above item 5) are discredited, receiving a score of 0.
  • After crediting and discrediting as above, the item scores are summed to give the test total score. The maximum total score for the test is 35.

Item Variables

The item variables relating to the TOAL 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.

The variable holding the total test score was also generated automatically on the web server, and therefore appears as an item variable in the raw data. However, because of errors in branching (caused by crashed items), the test total score is in fact re-computed, and is therefore effectively a derived variable. Variables representing the position of the basal and the ceiling are also derived, and are included in the table below for completion.

In most cases the values of these variables have been left unaltered, although some have been recoded during data cleaning:

• For timed out items, the item response variable is recoded from missing to -1, and the item answer time is recoded from 45 to missing (item scores are 0)
• The correct position of the ceiling is determined, and items above the ceiling are un-credited (if this has not already been done): item responses, which may or may not be missing, are recoded to -2; and item scores, which may be 0, 1 or missing, are recoded to 0.
• The correct position of the basal is determined, and items below the basal are credited (if this has not already been done): item responses, which may or may not be missing, are recoded to -3 unless the correct response is already recorded; and item scores, which may be 0, 1 or missing, are recoded to 1.
• For items that 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.
• Following the recoding of item scores above the ceiling or below the basal, as described above, the correct total test score is re-computed.
• For instances of crashed or otherwise compromised tests, 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. Note that this is not necessarily the same as the order in which items were presented to twins in the test (see test rules above).