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rshearn37
04-02-2003, 11:27 PM
Hello All,

Thank you to all who responded. You comments and suggestions were very
helpful.

A summary of responses is listed following the original query:

Hello All,

I am trying to quantify comfort for a comparison study on mattresses. The
test subject lays supine for a given amount of time and asked to rate their
amount of comfort. Besides the "smiley face" survey widely used in US
hospitals for pain levels (and associating a numerical value to each face)
and having the subject place a dash on a 10 cm line with one end being
extremely uncomfortable and the other end being extremely comfortable and
measuring the distance in cm to get a numerical value, are there any other
reliable methods/ surveys anyone has used successfully in the past?

I also have a version of a survey that identifies specific areas of the
body for evaluation (neck, shoulders, upper back, etc.) Right now I'm
investigating a combination of the three mentioned above and was wondering
if anyone can offer any guidance.

Any suggestions are most appreciated and I will post a summary of responses
if there is interest.

Thank you in advance,
Rebecca


-------------------------
Rebecca Shearn
Biomedical Engineer


*****************************************
Dear Rebecca,

Of the two you mentioned the line-marking technique is, in my opinion,
probably better. Another option is to use the classic psychophysical
technique of magnitude estimation. This involves having your subjects rate
a set of test objects (mattresses) relative to a standard mattress. The
standard mattress is assigned (by the experimenter, or by the subject) an
arbitrary comfort rating (e.g., 100 arbitrary "comfort units"). Subjects
rate the test mattresses relative to the standard. For example, if they
judge a mattress to be twice as comfortable as the standard, they would
give it a rating of 200, and if they judge another mattress to be half as
comfortable as the standard, they would give it a rating of 50. This
scaling method has some nice properties--e.g., magnitude estimation yields
a true ratio scale, rather than an ordinal (rank) scale, which gives you
better statistical analysis options.

There is a huge literature on this and other psychophysical methods that
might be useful to you. Try searching a literature database such as
PsychInfo with "magnitude estimation", "psychophysical methods", or
"psychophysics" as keywords. You might also turn to the large sensory
evaluation literature that emerged out of food science and is currently
being applied to a wide range of product testing.

Kind regards,
Mike

_____________________________________
Michael A. Riley, Ph. D.
Assistant Professor
Department of Psychology
ML 0376, 429 Dyer Hall
University of Cincinnati
Cincinnati, OH 45221-0376 USA

Office: 229-F Dyer Hall

P: 513.556.5544
F: 513.556.1904

http://www.oz.uc.edu/~rileym/pmdl/RileyLab/
michael.riley@uc.edu

*********************************************
Hi,

Following references may be useful for defining your comfort/discomfort
evaluation method. Hope this helps.

X. Wang



---------------------

Bonnet, C., 1986. Manuel pratique de psychophysique, Armand Colin Edition,
Paris. Borg, G., 1982. Psychophysical bases of perceived exertion.
Medicine and Science in Sports and Exercise, Vol.14, No.5, pp.377-381.
Buckle, P. and Fernandes, A. 1998. Mattress evaluation - assessment of
contact pressure, comfort and discomfort, Applied Ergonomics, vol. 29, No.
1, pp. 35-39. Corlett, E.N. and Bishop, R.P., 1976. A technique or
assessing postural discomfort. Ergonomics, Vol. 19, No. 2, 175-182.
Drury, C.G. and Coury, B.G., 1982. A methodology for chair evaluation.
Applied Ergonomics, 13, 195-202. Giacomin J., Quattrocolo S., 1997. An
analysis of human comfort when entering and exiting the rear seat of an
automobile. Applied Ergonomics, Vol 28, N° 5/6, pp397-406, 1997. Han, S.H.,
Song M., Kwahk, J., 1999. A systematic method for analyzing magnitude
estimation data. International Journal of Industriel Ergonomics, 23,
513-524. Helander, M.G. and Zhang, L. 1997. Field studies of comfort and
discomfort in sitting. Ergonomics, Vol.40, No.9, 895-915. Oborne D.J.,
Clarke M.J., 1973. The development of questionnaire surveys for the
investigation of passenger comfort, Ergonomics Vol. 16, 855-869. Shackel,
B., Chidsey, K.D. and Shipley, P. 1969, The assessment of chair comfort,
Ergonomics, 12, 269-306. Shen, W. and Parsons, K.C., 1997. Validity and
relaibility of rating scales for seated pressure discomfort. International
Journal of Industriel Ergonomics, 20, 441-461. Thomas, R.E., Congleton,
J.J., Hukington, R.D., Whiteley, J.R., Rodrigues, C.C., 1991. An
investigation of relationships between driver comfort, performance and
automobile seat type during short time driving tasks. International Journal
of Industriel Ergonomics, 8, 103-114. Zhang, L., Helander, M.G., Drury,
C.G., 1996. Identifying factors of comfort and discomfort in sitting. Human
Factors, 38(3), p377-389.

-------------------------------
________________________________________
M. Xuguang Wang, PhD
Chargé de Recherche
INRETS-LBMC
25 avenue François Mitterrand, Case 24
F-69675 Bron
France
Tél: 33-(0)4-72-14-24-51
Fax: 33-(0)4_72-14-23-60
Email: wang@inrets.fr


*****************************************
The reference cited below could be a useful resource.

Zhang, L. Helander, M. G., and Drury, C. G. (1996). Identifying Factors of
Comfort and Discomfort in Sitting. Human Factors, 38(3), 337 - 389.

*************************************
Just a few thoughts. Not sure what or who you are doing this for but when
we do usability testing we frequently focus on comfort, fit and
desirability (will the person buy the product). Manufacturers find this
information quite important.

Rather than a 10 scale, we commonly use a 7 point scale with a statement "I
find this mattress comfortable for my back" (polarized scale - strongly
agree to strongly disagree).

Measuring the values may be appropriate but I think that it would be easier
to do a straight forward comparison between models.
Have the users plot on something like this. From a consumer perspective,
the rank order for each characteristic is probably the most important
rather than the number itself.

Worst Best
Neutral

|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|

-10 -5 0
+5 +10


Dale Braun, B.Sc. (H.K.)
Interface Ergonomics
a BC Research Company
3650 Wesbrook Mall
Vancouver, B.C., V6S 2L2
Phone: 604-222-5566
Fax: 604-224-0540
http://interface-ergonomics.com
http://ergonomics.bcresearch.com
dbraun@interface-ergonomics.com

This e-mail may be privileged and confidential. Any use of this e-mail by
an unintended recipient is prohibited. If you receive this e-mail in error
please call us immediately.

*****************************************
This might help:

Mündermann A., B.M. Nigg, D.J. Stefanyshyn, and R.N. Humble (2002)
Development of a reliable method to assess footwear comfort. Gait &
Posture 16(1): 38-45.

Anne
__________________________________________________
Anne Muendermann, Ph.D.
Postdoctoral Fellow
Division of Biomechanical Engineering
Stanford University, CA
Tel. (650) 724-9684
Fax. (650) 725-1587
Email amuender@stanford.edu

*****************************************
There are also Likert scales - usually 5 or 6 point scales that I am sure
you
are familiar with (e.g. Very satisfied, somewhat satisfied, neither,
somewhat
disatisfied, very disatisfied, etc...) for whatever you want to associate
them
with. I think they may be as sensitive for you as the 10 point scales. It
may be a matter of how you want to analyze it - e.g. use a continuous
measure,
anywhere from 0 - 10 on a "ratio" scale with the line; or use an interval
scale from 1 - 5 or 1 - 10 with the discrete happy to sad faces and/or
Likert
scale. It may be easier to justify grouping those who chose "somewhat
satisfied" to "very satisfied" vs "neither' to very dissatisfied", rather
than
choosing to summarize who marked 7.5 cm or higher (or whatever cutoff you
choose) on a line as meaningful. I did a survey a few years back in which
I
modified previously validated questions regarding knee pain with various
functional activities for those using a knee brace. I initially made two
surveys, one with the line version and one with the 5 pt Likert scale
version.
I asked a pilot group to answer both and then indicate which they
preferred.
In general, they were highly correlated, as you would expect, and the
majority
liked the likert scale better than marking on a line. So, that is the
style
I ended up using. You can't of course use "traditional" stats with this
type
of data like means and stand dev. whichever version you choose as the
interval
between 1 and 2 vs. 3 and 4 may not really be "equal" or mean the same, but
you probably already knew that.
Good luck. Laura

Laura Frey Law
PhD candidate, Rehabilitation Science
University of Iowa

*****************************************
Rebecca:

I recommend that you examine the following article as a starting point.

Helander MG and Zhang L, "Field Studies of Comfort and Discomfort in
Sitting," Ergonomics, Vol. 40, No. 9 (1997), pp. 895-915.

The work performed by Helander and Zhang is quite extensive. They actually
suggest separating comfort from discomfort as they are not synonymous, but
complementary.

I hope this helps

Carmen


Carmen P. DiGiovine, PhD
Postdoctoral Research Associate
--
University of Illinois at Chicago
Assistive Technology Unit
Institute on Disability and Human Development
Department of Disability and Human Development
Department of Bioengineering
--
312-413-3113 (direct)
312-413-1555 (main)
312-413-3709 (fax)
312-413-1554 (tty)









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