Table 1.1 Distribution map

(controlled by MRANGE=, MAXPAGE=, T1I#=, T1P#=)

This table shows the distribution of the persons and items. The variable is laid out vertically with the most able persons, and most difficult items at the top.

TABLE 1.1 LIKING FOR SCIENCE (Wright & Masters p.18) SFO.TXT Dec 1 18:33 1996

76 PUPILS 25 ACTS REPORTED: 74 PUPILS 25 ACTS 3 CATEGS v2.67

76 PUPILS 25 ACTS Number of persons in data file and items in NI= specification.

ANALYZED: 74 PUPILS 25 ACTS 3 CATEGS Number of persons, items and categories that with non-extreme scores.

v2.67 Winsteps version number.

MAP OF KIDS AND TAPS

MEASURE | MEASURE

5.0 + X 5.0

| XXX (items too hard for persons)

4.0 + 4.0

XX |

| X

3.0 + 3.0

X |

| X

2.0 XXXX + 2.0

| X

1.0 XXXXX + 1.0

| X

.0 + .0

XXXXXXXXXXXX | (gap!)

-1.0 + -1.0

XXX |

| X

-2.0 + -2.0

XX | X

X | X

| XX

-3.0 XX + X -3.0

In Table 1, each person or item is indicated by an "X", or, when there are too many "X"s to display on one line, several persons or items are represented by a "#". Less than that number by ".". So that if "#" represents 4, then "." represents 1 to 3.

The left-hand column locates the person ability measures along the variable.

For dichotomous items, the right-hand column locates the item difficulty measures along the variable. Look for an even spread of items along the variable (the Y-axis) with no gaps, indicating poorly defined or tested regions of the variable. The persons often show a normal distribution. Good tests usually have the items targeted (lined up with) the persons.

For polytomous items, Table 2.2 shows the operational range of the item with its rating scale.