TEDS Data Dictionary

Description of Test

This was a modified version of the General Knowledge test that was used in the 10 Year study. The items themselves are unchanged; however the branching rule has been modified so that twins enter the test at a higher level of difficulty. There is a slight modification in the discontinue rule, affecting the point at which the rule starts to apply.

The test consists of a series of general knowledge questions. For each question, there are four possible responses; the twin selected a response by clicking on it on the screen. There are 30 items: the questions and responses are tabulated below. Any given twin taking the test may have been presented with fewer than 30 items, because of the branching and discontinue rules, which are described 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 is 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 general knowledge.

This test was unaffected by item timeouts.

Test Rules

• Scoring
  For each question, the correct response is given a score of 1, and any of the three incorrect responses is given a score of 0. The maximum total score for the test is 30.
• Branching rules
  
  • Start at item 9, and proceed to item 10.
  • If both items 9 and 10 are correct (scoring 1 each), give credit for items 1-8 (as though they had been answered correctly, gaining a score of 1 for each item), then proceed upwards from item 11.
  • If either item 9 or item 10 is incorrect (scoring 0), attempt the lower items (1-8) in reverse order. Then:
    • If any two successive items are correct (e.g. 8 and 7), then give credit for any of items 1-8 not yet attempted; then proceed upwards from item 11. Note that if either item 9 or item 10 is correct, and this is followed by a correct answer for item 8, then this results in an upward branch to item 11 (items 10 and 8 are treated as successive items, as are items 9 and 8, for this rule).
    • If no two successive items are correct, the test ends after item 1 has been attempted.
• Discontinue rule
  Discontinue the test after five scores of zero in any six consecutive items. This rule only applies from item 11 upwards. It does not include the branching items (9 and 10), nor does it include the lower items (1-8) if attempted.

Item Variables

The item variables relating to the General Knowledge 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 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 table below, equates to the numbering used in the item variables. Note that this is not the same as the order in which items were presented to twins in the test (see branching rules above).

item	question	response A	response B	response C	response D	correct response
1	What do you call this?	Neck	Toes	Eyes	Nose	D
2	How many ears do you have?	1	2	3	4	B
3	How many legs does a dog have?	2	3	4	5	C
4	What is the day that comes after Thursday?	Monday	Tuesday	Wednesday	Friday	D
5	What must you do to make water boil?	Heat it	Put water in it	Put eggs in	Stir it	A
6	Name two kinds of coins	French and German	Pound and Penny	Queen and Flower	Money and Five Pound Note	B
7	What month comes right after March?	April	May	June	February	A
8	How many days are there in a week?	2	5	7	10	C
9	What are the four seasons of the year?	Summer, Autumn, Winter, Spring	Halloween, Mother’s Day, Christmas, Easter	Sunny, Rainy, Windy, Snowy	Hot, Warm, Cool, Cold	A
10	How many things make a dozen?	Six	Twelve	Eggs	Ten	B
11	How many hours are there in a day?	8	12	24	60	C
12	What does the stomach do?	Digests food	Growls	Breathes	Swallows	A
13	Who was Christopher Columbus?	He was president	He was a pilgrim	He discovered America	He was an inventor	C
14	Name three oceans	Salt Lake, Nile, Gulf of Mexico	River, Lake, Sea	Indian, Pacific, Atlantic	Stream, Pond, Creek	C
15	Which month has one extra day every four years?	January	February	May	December	B
16	In what direction does the sun set?	North	East	South	West	D
17	How is oxygen returned to the air?	By breathing	By plants	By the wind	By clouds	B
18	On what continent is Brazil?	South Africa	Asia	South America	Europe	C
19	What is water made of?	Hydrogen and oxygen	Rain	Helium and oxygen	Minerals and chemicals	A
20	Who invented the electric light bulb?	Albert Einstein	Thomas Edison	Benjamin Franklin	Thomas Jefferson	B
21	What country in the world has the largest population?	Africa	Russia	New York	China	D
22	Who was Anne Frank?	A singer	A pilot	A girl who wrote a diary	A teacher of deaf and blind	C
23	What are hieroglyphics?	Ancient Greek letters	Roman numerals	Egyptian picture writing	Cave paintings	C
24	What is the main material used to make glass?	Plastic	Sand	Hydrogen	Fibreglass	B
25	What is the capital of Greece?	Rome	Cairo	Crete	Athens	D
26	What causes iron to rust?	Acid	Oxygen	Salt	Minerals	B
27	What is a barometer?	It measures rainfall	It measures wind speed	It measures air pressure	It measures earthquakes	C
28	Who was Charles Darwin?	He was a poet	He discovered the structure of DNA	He was a character in a Dickens novel	He developed the theory of evolution	D
29	How far is it from London to New York?	200 miles	3,000 miles	9,000 miles	40,000 miles	B
30	What does turpentine come from?	Conifer trees	Varnish	Acid	Ethyl Alcohol	A