TEDS Data Dictionary

The 16 Year Problem Verification Task (PVT) Web Test

Contents of this page:

Introduction

This page describes the Problem Verification Task (PVT) test, which was included in the 16 Year twin web study.

Description of Test

The image below is an example item from the PVT test:
PVT example screen
Every item is presented in the same format: a mathematical equation is shown near the top of the screen, and twins have 10 seconds to try to decide whether the equation is correct or incorrect.

To respond, twins must press a keyboard key (F, J or K). They are asked to press F if they think the equation is right, J if they think it is wrong, or K if they simply don't know. After the twin presses F, J or K, the next item automatically appears on screen.

If no response is given within 10 seconds, then the item times out. The item is then forfeited with zero score. A "next question" screen then appears, and the twin must click on this in order to resume the test at the next question.

In the test introduction, the twins are asked to attempt 2 practice items before they proceed to the main test, with feedback to tell them whether they gave correct responses (no feedback is given in the main test). Twins may repeat the practice items before they start the main test if they wish.

The main test consists of 48 items. Items are presented in item number order, from 1 to 48, without any branching or discontinue rules. Because of the large number of items, twins are given one opportunity to "come back later", i.e. to pause the test and resume at a later time - this opportunity appears after item 24. To avoid disrupting the flow of the test, the "come back later" option is not presented at any other times. The items are presented in full in the table below.

Test Rules

  • Scoring
    For each item, the correct response is given a score of 1, and any other response (including the K=don't know response) is given a score of 0. The total test score is the sum of the item scores. The maximum total score for the test is 48.
  • Timeout rule
    A timeout of 10 seconds applies to each item. After 10 seconds with no response, the item is forfeited with zero score, and the intermediate screen appears asking the twin to continue with the next item.
  • Responses
    Only the keyboard keys F, J and K will register any response. Responses are recorded in coded form as 1=F, 2=J, 3=K or 4=timed out in the raw data.

Item Variables

The item variables relating to the PVT 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.

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 timed out items, the item response variable is recoded from 4 to -1, and the item answer time is recoded from 10 to missing (item scores are 0)
  • 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 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.

VariablesExplanationValues
pcpvstat1/2 Status flag: outcome of test 0=not started, 1=started but not finished, 2=successfully completed, 4=random responses
pcpvdata1/2 Data flag: is test data present? 0=no, 1=yes
pcpvtot1/2 Total score for this test, out of 48. 0 to 48 (integer values)
pcpvquan1/2 Number of questions answered in the test integer values up to 48
pcpvstdt1/2 Start date of the test [not in dataset] Date values
pcpvsttm1/2 Start time of the test [not in dataset] Time values
pcpvendt1/2 End date of the test [not in dataset] Date values
pcpventm1/2 End time of the test [not in dataset] Time values
pcpvsess1/2 Number of sessions (at the computer) used by the twin to complete the test. Integer values of 1 or above
pcpvtmel1/2 Total time elapsed during the test, in seconds Integer values (number of seconds)
pcpvXXan1/2
(XX is the item number, 01 to 48)
Item response 1=F (right), 2=J (wrong), 3=K (don't know), or -1=timeout, -4=item crashed
pcpvXXsc1/2
(XX is the item number, 01 to 48)
Item score 1=correct, 0=incorrect or don't know or timed out
pcpvXXat1/2
(XX is the item number, 01 to 48)
Answer time: length of time (in seconds) taken by the twin to respond to this item [not in dataset] Decimal values, recorded to 3 decimal places (seconds, between 0 and 10)
pcpvXXdt1/2
(XX is the item number, 01 to 48)
Download time: length of time (in seconds) between the end of the previous item and the start of this item; time needed to download files for this item [not in dataset] Decimal values, recorded to 3 decimal places (seconds)

Test Items

Item no.Equation imageCorrect response
1PVT test item 1 J (wrong)
2PVT test item 2 F (right)
3PVT test item 3 J (wrong)
4PVT test item 4 F (right)
5PVT test item 5 F (right)
6PVT test item 6 J (wrong)
7PVT test item 7 F (right)
8PVT test item 8 J (wrong)
9PVT test item 9 F (right)
10PVT test item 10 F (right)
11PVT test item 11 F (right)
12PVT test item 12 F (right)
13PVT test item 13 J (wrong)
14PVT test item 14 F (right)
15PVT test item 15 F (right)
16PVT test item 16 F (right)
17PVT test item 17 J (wrong)
18PVT test item 18 J (wrong)
19PVT test item 19 J (wrong)
20PVT test item 20 J (wrong)
21PVT test item 21 J (wrong)
22PVT test item 22 J (wrong)
23PVT test item 23 F (right)
24PVT test item 24 F (right)
25PVT test item 25 J (wrong)
26PVT test item 26 F (right)
27PVT test item 27 J (wrong)
28PVT test item 28 F (right)
29PVT test item 29 F (right)
30PVT test item 30 J (wrong)
31PVT test item 31 J (wrong)
32PVT test item 32 J (wrong)
33PVT test item 33 J (wrong)
34PVT test item 34 F (right)
35PVT test item 35 J (wrong)
36PVT test item 36 F (right)
37PVT test item 37 F (right)
38PVT test item 38 F (right)
39PVT test item 39 J (wrong)
40PVT test item 40 F (right)
41PVT test item 41 J (wrong)
42PVT test item 42 J (wrong)
43PVT test item 43 F (right)
44PVT test item 44 F (right)
45PVT test item 45 J (wrong)
46PVT test item 46 J (wrong)
47PVT test item 47 F (right)
48PVT test item 48 J (wrong)