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Bond, Yan, Heene (2020) Applying the Rasch Model 4th Edition
Bond & Fox (2015) Applying the Rasch Model, 3rd Edition
Bond & Fox (2007) Applying the Rasch Model, 2nd Edition
Click here for a comparison of the functionalty of Bond&FoxSteps compared with Winsteps and Ministep
Bond & Fox (2001) Applying the Rasch Model, 1st Edition ...
Chapter 6: Computer Opinion Survey
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.
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B&F Computer Opinion Survey data p. 75
The entire dataset is obtained from www.facebook.com/ApplyingTheRaschModelBondFox.
The original data set contains 26 items and 273 children. This exceeds
the MINISTEP maximum of 25 items and 75 persons, so the 26th item and last 198 persons are not analyzed.
Highlight with your mouse from here >
Title = "B&F CAIN Computer Anxiety Index: 26 items"
Item1 = 3 ; Response to first item is in column 3
NI = 26 ; 26 items used.
Name1 = 1 ; Person identifier starts in column 1
Xwide = 1 ; Each observation is 1 columns wide
IREFER= FFFFRFRFRFRRFRFFFRRRRRRRRF ; two types of item: F = Forward, R = Reverse
Codes = 123456 ; valid codes 1-6.
IVALUEF=123456 ; Forward (positive) items
IVALUER=654321 ; Reversed (negative) items
cfile=* ; label the scored rating scale categories
1 Strongly Agree
2 Agree
3 Slightly Agree
4 Slightly Disagree
5 Disagree
6 Strongly Disagree
*
Total = Yes ; show total raw scores
Chart = Yes ; produce across-pathway picture
Mnsq = No ; use Standardized fit statistics
Uimean= 0 ; Item mean difficulty at 0.
Stbias= Yes ; Adjust for estimation bias
&End
01 Available ; Item labels are original CAIN item numbers
02 Time-saver ; Please use item text, where possible!
03 Conceptualize
04 Better
05R Not enjoy ; R="reversed" - to remind ourselves!
06 Easier
07R Negative
08 Fun
09R Dump
10 Anticipate
11R Not use
12R Avoid
13 Enjoy
14R Excessive
15 Important
16 Learning
17 Satisfy
18R Trouble
19R Uncomfortable
20R Nervous
21R Unlearnable
22R Complicated
23R Unhappy
24R Intimidated
25R Overwhelming
26 Useful
END NAMES
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< to here. Then Copy.
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.
"Save as"
Go to the C:\WINSTEPS directory
File Name: CAIN.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 CAIN.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.
Ministep reports "Measures constructed"
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B&F Figure 6.2 paralled p. 76
Click on the "Output Tables" pull-down menu
Click on "13. ITEM Measure". The Table displays.
Scroll down to Table 13.2. This approximates Fig. 6.2, which obtained
from a larger sample.
Thresholds are not shown in Table 13.2.
To see the thresholds,
Click on the "Output Tables" pull-down menu
Click on "2.0 Measure forms (all)". The Table displays.
Scroll down to Table 2.3 to see the B&F Thresholds.
This Table shows the measurement system horizontally, with each item on a separate
line.
The "thresholds", sometimes called "Thurstone Thresholds" (though not estimated
according to Thurstone's method)
are the points at which there is a 50% probability of being observed in categories
below and 50% being observed in categories above the category transition point.
In this plot, each thresholds is identified by the category to its right (i.e., higher
up the measurement scale.)
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B&F Table 6.2 p. 77-8
In Table 6.2, the "Taus", i.e., the Rasch rating scale structure parameters,
are the same for every item. To see them,
Click on the "Output Tables" pull-down menu
Click on "3.2 Rating Scale Structure". The Table displays.
In the second panel there is the "STRUCTURE". The "Measure" column corresponds
to the first row of the "Taus", and the "S.E." column to the "Error" row.
Now for the item-level statistics:
Click on the "Output Tables" pull-down menu
Click on "13 Item measure". The Table displays.
The item measures, errors, and fit statistics are shown. The order is slightly
different to B&F because the last 73 people were not included in the anaysis.
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B&F Fig. 6.3 p. 80
Click on "02"on your Task bar or
Click on the "Output Tables" pull-down menu
Click on "2 Measure forms (all)". The Table displays.
Scroll down to Table 2.4
In Fig. 6.3, each item is a column. In Table 2.4 each item is a row.
In Table 2.4 the person distribution is shown beneath the Table, with the frequencies
displayed vertically so that
32
734
means 37, then 23, then 4
In Fig. 6.3, the "Thresholds" are now the rating scale structure parameters or "Taus."
(This ambiguous use of the word "Threshold" is common in the literature.)
These parameters are not usually pictured in this way, because they have a pairwise,
rather than global meaning. When put in a picture like this, we automatically
interpret them globally, and start to be concerned that the category numbers
are "disordered".
To verify that the categories themselves are order,
Click on the "Output Tables" pull-down menu
Click on "3.2 Rating scale structure". The Table displays.
Look at the "Obsvd Avrge", Observed Average Measure, column. These report the average
(person ability-item difficulty) measures of those who chose each category.
They are in order except for a slight wrinkle between categories 5 and 6.
Click on "02" on your Taskbar, and investigate this further by looking at Table 2.6.
"OBSERVED AVERAGE MEASURES BY OBSERVED CATEGORY FOR PERSONS"
We expected to see "123456" for the forward items, and "654321" for the reversed items.
The itemes with "R" in their labels are indeed reversed.
Some items, such as item 13, have their categories in order, but most don't. Why?
Click on the "Output Tables" pull-down menu
Click on "23. ITEM: principal components". The Table displays.
This Table looks for stucture in the items that is not explained by one underlying dimension.
Scroll down to Table 23.3.
Above the dividing line, only one item has an "R". Below the dividing line
nearly all items have an "R". There is something different about the reversed items.
Perhaps some responded failed to notice they were reversed. Perhaps the
the forward items correspond to acceptance and the reversed items to rejection,
and they are not exact opposites. Here is a fruitful area to launch a qualititative
analysis of the items and the respondents. But note that
"Yardstick (variance explained by measures)-to-This Factor ratio: 7.0:1"
This means that the forward-reverse item effect is only 1/7th the size of
the main dimension - not usually enough to motivate two separate instruments.
But we can always analyze the forward and reverse items separately, to see what
happens.
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