TEDS Data Dictionary

Description of Test

Each item of this test displayed four shapes, one of which had been divided into several jigsaw pieces; the twin had to decide which of the four shapes would match the assembled jigsaw pieces. To select an answer, the twin simply clicked on the chosen shape. There was a time limit of 2 minutes for each item. There were 28 items, which are displayed in full in the table of test items at the bottom of this page. The test had branching and discontinue rules, which are explained below under the heading test rules.

Changes were made to the test at the end of wave 1, because of perceived problems with internal consistency and reliability in the results. It was felt that the items, as numbered, were not in the correct order of ascending difficulty as required; this led to unwanted effects from the branching and discontinue rules. In an attempt to improve the test, the items were re-ordered. The items themselves are the same, but their numbering was changed. The item numbering both for both versions (wave 1 and wave 2) are shown in the table of test items below. This means that dataset item variables for a given item number refer to different items, for wave 1 twins and wave 2 twins.

The test was originally designed to have a 2-minute item timeout rule. However, in practice, the test items in the data are entirely unaffected by item timeouts.

Test Rules

• Scoring
  For each question, a correct response is given a score of 1, and any of the three incorrect responses is given a score of 0.
  Where items are skipped due to upward branching, they are credited with a score of 1 as if they were answered correctly.
  The maximum total score for the test is 28.
• Branching rules
  Note that the items referred to in these rules are different in wave 1 and wave 2, because of the change in item numbering (as explained above).
  • Start with items 9, 10 and 11.
  • If items 9, 10 and 11 are all incorrect, go to item 1. Attempt the remaining items (1-8 and 12-28) in ascending numeric order.
  • If at least one of items 9, 10 and 11 is correct, credit items 1-8 as though they had been answered correctly. Proceed with items 12-28 in ascending numeric order.
• Discontinue rule
  Discontinue the test after three consecutive incorrect answers. This rule applies to all except the branching items (9, 10, 11). Items either side of the branch (items 7,8,12,13) are treated as consecutive for a twin who has branched down; for example, such a twin would discontinue if items 7, 8 and 12 were answered incorrectly.

Item Variables

The item variables relating to the Jigsaws 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 also that the variable holding the total test score was also generated automatically on the web server, so this is treated as an item variable, not a derived variable.

The items were re-ordered between wave 1 and wave 2, so that the item numbers changed (see table of test items at the bottom of this page). This means, for example, that the item variable ljg01an1 holds responses for item 8-9/9 for wave 2 twins, while it holds responses for item 8-9/3 for wave 1 twins.

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 skipped and credited due to upward branching, the item response variable is recoded from missing to -3 (the item score is already recorded as 1 on the web server).
• 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.
• 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 first two columns of the table below, equates to the numbering used in the item variables; but note that the numbering changed between wave 1 and wave 2. In each wave, the order in which items were presented to twins varied according to the branching rules (see test rules above).

The reference column gives the booklet and item number in the original form of the test. Each reference has the form X-Y/Z, where X-Y is the booklet age range (8-9 or 12-14), and Z is the item number within the booklet.

wave 2 item	wave 1 item	reference	jigsaw image and answer options (numbered 1,2,3,4 left to right)	correct answer
1	5	8-9/9		2
2	3	8-9/5		1
3	8	8-9/12		4
4	1	8-9/3		4
5	4	8-9/6		2
6	2	8-9/4		2
7	6	8-9/10		3
8	7	8-9/11		1
9	9	8-9/13		3
10	17	12-14/5		3
11	16	12-14/4		1
12	14	12-14/2		4
13	24	12-14/12		2
14	20	12-14/8		1
15	13	12-14/1		3
16	22	12-14/10		4
17	10	8-9/14		4
18	11	8-9/15		1
19	27	12-14/15		1
20	19	12-14/7		4
21	12	8-9/16		3
22	18	12-14/6		2
23	15	12-14/3		2
24	23	12-14/11		1
25	25	12-14/13		4
26	28	12-14/16		2
27	21	12-14/9		2
28	26	12-14/14		3