[Rasch] Logit scores
barthr at uic.edu
Wed Dec 21 07:27:11 EST 2005
I have encountered this problem myself. While 0-100 is a nice "intuitive"
scoring convention, it's resemblance to percentages is problematic. Perhaps
another scaling range would avoid this problem. Another approach would be to
create criterion-based norms by having clinical experts identify the ranges
for low, medium, high satisfaction. Showing a variable map might also help
to provide a context for the measurements. The interpretation of change
along a measurement needs to take into consideration whether we are talking
about individual change or group/sample change. While it may be possible for
an individual's measure to increase from say, 50-60 up to an 80-90, mean
change of this magnitude is far less likely for a group (e.g., hospital
unit). How one conveys this to end users is another question!
Barth Riley, Ph.D.
Res. Asst. Professor & Associate Program Director
Dept. of Disability and Human Development M/C 626
University of Illinois-Chicago
1640 W. Roosevelt Rd.
Chicago, IL 60608
Voice (312) 355-4054
Fax: (312) 355-4058
Email: barthr at uic.edu
From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au] On Behalf
Of Lee, Wynne
Sent: Tuesday, December 20, 2005 1:01 PM
To: Mike Linacre (RMT); Rama Guinda; rasch at acer.edu.au
Subject: RE: [Rasch] Logit scores
I work at PeaceHealth, a health care organization with 6 hospitals and
numerous clinics. We routinely used Rasch-based measures of patient
satisfaction for several years now, doing what Mike suggested: transforming
logits to "zero - 100" scores. It's a great, logical, rational and easily
However, there's a real challenge with this transformation. Our patient
satisfaction scale is very good. Of the 2000-odd patients we survey every 6
months, there are some who report near-perfect scores and some near the
bottom, but most most fall somewhere around the middle (as distributions
The challenge with the "zero-100" representation is that many units for
which we issue reports now get scores in the 50 - 75 range. Most people in
the medical world are highly educated in very competitive environments. They
are used to getting very high grades ... typically 90%+. So, receiving
patient satisfaction scores of 50-70 feels like failing. PeaceHealth has
tried, over the years, many strategies, metaphors, discussions, images etc
to move people away from that feeling. It also does not reward particular
score levels, but rewards improvements in scores over time. That is, shifts
from 25 to 28, 45 to 48 or 75 to 85 are equally valued & rewarded.
Despite those efforts, managers who get the reports often struggle when they
hear their unit's score moved to 62.1, up from 58. It still feels like
failure or 'barely passing'. That feeling is augmented by having friends at
other hospitals that use non-Rasch based commerical patient satisfaction
surveys, who often get nice, high scores like 85 or 90! Competitive urges
(and economics) combined with years of conditioning to think that only
scores > 80 are really "good" takes a real psychological toll.
Maybe this is just a problem for health care organizations. Has anyone else
run into this challenge? Found a work-around?
Wynne A. Lee, Ph.D.
Data Analyst, Survey Team
HID Continuous Improvement Division, PeaceHealth
Bellingham, WA 98225-1898
Tel. (360) 738-6300 X4581
Email: <mailto:wlee at peacehealth.org>
There can be no happiness if the things we believe in are different from the
things we do. Freya Stark
From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au]On Behalf
Of Mike Linacre (RMT)
Sent: Monday, December 19, 2005 8:46 AM
To: Rama Guinda; rasch at acer.edu.au
Subject: Re: [Rasch] Logit scores
How about linearly transforming logits into the range 0-100 for the lowest
to highest possible measure on the test? Then the Rasch measures mean "per
cent of the way up the test".
What transformations have other folks found useful?
Rama Guinda wrote:
How to report the logit scores in the form of understandable and meaningful
scores for the students, parents and teachers?
Scores that are easy to make sense of and at the same time maintain the
interval characteristic of the logit scores.
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT: 19:3 Winter
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