Bond & Fox (2001) Applying the Rasch Model ...

Chapter 2: Math Curriculum Example

You will need to read the text of the book to understand these examples. Official authors' website: Bond & Fox
Winsteps numerical results may differ somewhat from those in Bond & Fox due to differences in estimation procedures.

Statistics.com Rasch Course participants: Please see the Course instructions for a more detailed walk-through of this example.

To use Ministep, follow this procedure:

Download and install the free program, Ministep.

B&F Table 2.1 p. 12

For convenience of data entry, we replace "" by "r".

Highlight with your mouse from here >

Title = "B&F Table 2.1 Math Curriculum"
Item1 = 3        ; Response to first item is in column 3
NI    = 12       ; Number of items is 12, items a-l
Name1 = 1        ; Person identifier starts in column 1
Xwide = 2        ; Each observation is 2 columns wide
Codes   ="r X "  ; valid codes are "r " and "X "
Newscore="1 0 "  ; r scored 1, and X scored 0
Total = Yes      ; show total raw scores
&End
a 37+2 ; 12 item labels, one per line
b 56+4 ; Please use item text, where possible!
c 1+4  ; so I've added some dummy item text
d 27.3+34.09
e 4 1/4 + 2 1/8
f 2/4 + 1/4
g 4 1/2 + 2 5/8
h 86+28
i 6+3
j $509.74+93.25
k 2391+547+1210
l 7+8
; a b c d e f g h i j k l Score ; a comment to help read the data section.
END LABELS
A r r r X X X X r r X X r 6
B r X r r X X X X r X X X 4 
C r r r X r X X r r r r r 9
D r X r r X X X X r X X r 5 
E X r r X X r X r r r r r 8 
F r r r r X X X r r X X r 7 
G r X r X X r X X r X r r 6
H r X r X X X X X X X X r 3
I r r r r X X X r r X X r 7
J r r r r r r r r r X r X 10 
K r X r X X r X X r X r r 6 
L X r r X X r X r r r r r 8 
M X X X X X X X X X X X X 0
N r r r r r r r r r r r r 12

Start Ministep.
Do not answer the "Control File Name?" question.
Go immediately to "Edit" pull-down menu.
Click on "Edit/Create File with WordPad"
WordPad screen opens.
"Paste Special" as "Unformatted Text" what you just copied above.

It should look exactly like the block above.
The first section, up to &End, are control instructions.
The middle section, up to End Labels, are item labels.
The last section is the data. It has one person per line, and each item has its own columns.
Anything after a ";" is a comment, and is ignored by Ministep (except in the data).

"Save as"
Go to the C:\WINSTEPS directory
File Name: Table21.txt
Save as type: Text document
"Save"
"You are about to save the document in a Text-Only format ..."
Click "Yes"

Click on Ministep or Winsteps on the bottom of your screen
"Control File Name?" displays.
Press the Enter key
Find Table21.txt in the file list.
Click on it.
Click "Open"

"Report output file name ..."
Press the Enter key

"Extra specifications ..."
Press the Enter key

Ministep runs.
If it does not,
go to the Edit pull-down menu
"Edit Control File"
Does the Control file look like what you copied above?
If not, you may not have saved the file in text format.
In any case, please start again.

Ministep reports "Measures constructed"

Check the person raw scores in B&F Table 2.1
"Output Tables" pull-down menu.
Table 18 (in the center): Persons in Entry order.
Check that person raw scores agree with B&F Table 2.1
Close unneeded Ministep output Tables so they don't clog up your computer.

B&F Table 2.2 p. 13
"Output Tables" pull-down menu.
Table 22 (upper right): Scalograms.
Persons and Items are shown by entry number. Responses by 1 for "" and 0 for "X"

B&F Table 2.3 p. 15
First we need to delete extreme scoring person M with a zero score, and person N with a perfect score.
Go to the "Specification" pull-down menu
Type in:
pdelete= 13 14
Press OK
On the screen, it reports:
pdelete= 13 14
CURRENTLY REPORTABLE PERSONS = 12

Click on "Output Tables" pull-down menu.
Table 22. Scalograms

The two extreme people have disappeared.
But now we see that Item 3, c, at the left is extreme. Everyone succeeded on it. So delete that.

Click on "Output Tables" pull-down menu.
Table 22. Scalograms
This should match Table 2.3

Figure 2.1 p. 18

We can force Ministep to compute simple log-odds for the persons, like those shown in Figure 2.1

Go to the Edit pull-down menu
"Edit Control File"
If it does not open, it may already be on your Task Bar at the bottom of the screen as "Table ...". If so, click on it.

Position the cursor at the start of &End.
Press the Enter key to insert a blank line. Type >

pdelete = 13 14   ; delete extreme persons
idelete = 3       ; delete extreme item
iafile=*     ; this is the start of an "item anchor file" sublist.
1-12 0       ; this fixes all items (1-12) at a difficulty of 0 logits
*            ; this is the end of the list
maxpage = 40 ; control length of Table 16

"Save" this file.
Click on Ministep on the bottom of your screen.
"File" pull-down menu.
"Exit, then Restart ..."
Your old Ministep run will be closed, and a new one started.

"Report output file name ..." Press the Enter key
"Extra specifications ..." Press the Enter key
"Output Tables" pull-down menu.
Table 16. Person map
This should match the right side of Figure 2.1

Congratulations on reaching this far. You are well on your way!

In the next examples we will give much briefer instructions.
Rerun this example if you ran into difficulties.
Experiment with looking at some of the other Output Tables and Ministep program features.

Next Bond & Fox Tutorial
Index to Bond & Fox Tutorials