Measurement scales and depression
Robert A. Cummins
Australian Centre on Quality of Life
Deakin University
http://www.deakin.edu.au/research/acqol
Overview
What are the issues under investigation?
(a) The problem of sub-optimal response scales
(b) The problem of sub-optimal depression sales
Why are these issues important?
(a) Likert scales are blunt instruments
(b) We seem not to understand what depression actually is
What are the implications?
(a) Our response scales may be compromising our measurements
(b) We may be misdiagnosing depression
Freyd, M. (1923). The graphic rating scale. Journal
of Educational Psychology, 14, 83-102.
For job interviews
Does he appear neat or slovenly in his dress?
Extremely neat
and clean. Almost
a dude.
Appropriately and
neatly dressed.
Inconspicuous
in dress.
Somewhat
careless in his
dress.
Very slovenly
and unkempt.
“When you have satisfied yourself on the standing of this person
in the trait on which you are rating him, place a check at the
appropriate point on the horizontal line.
You do not have to place your check directly above a descriptive
phrase. You may place your check at any point on the line.” (p.88).
[then standardized to 0-10]
Rensis Likert
Head
Survey Research Center
University of Michigan
1903 - 1981
1
Strongly
approve
Likert, R. (1932) A technique for the measurement of attitudes.
Archives of Psychology, No.14, New York.
2
Approve
3
Undecided
4
Disapprove
Why only five levels of choice?
5
Strongly
disapprove
Problem #1
1. People can make more than five points of
discrimination. They are therefore blunt
instruments, not capturing the full extent of
discrimination
Increasing the number of choice points
above 5 increases scale sensitivity
• Diefenbach, M.A., Weinstein, N.D., & O’Reilly, J. (1993).
Scales for assessing perceptions of health hazard
susceptibility. Health Education Research, 8, 181-192.
• Russell, C., & Bobko, P. (1992). Moderated regression
analysis and Likert scales: Too coarse for comfort. Journal
of Applied Psychology, 77, 336-342.
• Jaeschke, R., & Guyatt, G.H. (1990). How to develop and
validate a new quality of life instrument. In: B. Spilker
(Ed.) Quality of life assessment in clinical trials (pp.4757). New York: Raven Press.
Problems with Likert scales
1. People can make more than five points of
discrimination. They are therefore blunt instruments
2. The number of choice points cannot easily be
expanded because we do not have the necessary
adjectives
Roy Morgan Research (1993)
Delighted
Very
pleased
Pleased
Mostly
satisfied
Mixed
feelings
Roy Morgan Research (1993). International values audit, 22/23 May.
Melbourne: Roy Morgan Research Centre.
Mostly
dissatisfied
Unhappy
Very
unhappy
Terrible
Problems with Likert scales
1.
People can make more than five points of discrimination.
They are therefore blunt instruments
2.
The number of choice points cannot easily be expanded
because we do not have the necessary adjectives
3.
The psychometric distance between the named adjectives
does not accord with the interval nature of the scale
Ware and Gandek (1994) used the Thurstone
method of equal-appearing intervals to
calculate the following distances between
category labels used in the SF-36
Actual
psychometric
separation
Poor
Fair
Good
Very
good
1.0
2.3
3.4
4.3
Ware, J. E., & Gandek, B. (1994) The SF-36 Health Survey: Development and use in mental health research and the IQOLA project.
International Journal of Mental Health, 23, 49-73.
Excellent
5.0
Louis Leon Thurstone
(1887 -1955)
Dept Psychology
University of Chicago
Jones, L.V., & Thurstone, L.L. (1955) The psychophysics
of semantics: An experimental investigation.
The Journal of Applied Psychology, 39(1), 31-36.
11-point, end-defined scale
Completely
Dissatisfied
0
1
Completely
Satisfied
Mixed
2
3
4
5
6
7
8
9
10
Can people reliably use 11-points of discrimination?
40
35
How satisfied are you with your
life as a whole?
33.1
N≈30,000
30
25
Frequency 20
17.9
17.1
15.1
15
10
7.0
5
0.5
0.3
0.6
1.2
1.7
0
1
2
3
4
5.5
0
5
Response scale 0 - 10
6
7
8
9
10
Critical issue #2
The relationship between SWB and
depression
Can the Subjective Wellbeing, or Positive
Affect, be used as a measure of
depression?
Dominant Source of SWB Control
Homeostasis
Set
point
Challenging
conditions
Defensive range
80
Set
Point
range
a
70
b
Upper
Threshold
SWB
Strong homeostatic defense
Lower
Threshold
c
Lower
Threshold
50
No
challenge
Strength of challenging agent
Very strong
challenge
Theoretical
proposition
a
b
Upper
Threshold
Strong homeostatic defense
Lower
Threshold
Lower
Threshold
c
Loss of positive
wellbeing= depression
Positive wellbeing is controlled by a homeostatic process
Homeostatic defeat means positive wellbeing is lost
Depression is the loss of positive wellbeing
The measurement of positive wellbeing should be THE
measure of depression
Is this idea consistent with (DSM-IV)
(a)
?
Symptoms of depression include the following:
depressed mood (such as feelings of sadness or
emptiness)
(b)
reduced interest in activities that used to be enjoyed,
sleep disturbances (either not being able to sleep well or
sleeping to much)
(c)
loss of energy or a significant reduction in energy level
(d)
difficulty concentrating, holding a conversation, paying
attention, or making decisions that used to be made fairly
easily
(e)
suicidal thoughts or intentions.
Depression is--(a) Loss of positive affect due to homeostatic
failure
(b)reduced interest
(c) loss of energy
(d)difficulty concentrating
(e) suicidal thoughts
These are just the
consequential symptoms
caused by the loss of
positive affect
How do we establish that
loss of positive wellbeing = depression?
How do the measures of depression and SWB
relate to each other?
r ≈ .7
How do the distributions of population incidence match?
40
35.3
35
30
26.5
25
Frequency
19.1
20
4.4%
15
10
7.4
7.3
5
2.8
0
0.1
0.4
0-10
11-20
21-30
1.1
0
31-40
41-50
51-60
61-70
71-80
81-90
Percentage points of SWB
Incidence of depression in Australia
Commonwealth Department of Health and Aged Care (2000)
5.8%
1997 National Survey of Mental Health and Wellbeing
6.0%
91-100
The relationship between SWB and depression (symptoms)
follows the theoretical pattern prescribed by homeostasis.
80
79.7
77.7
76.0
74.4
75
72.0
70.9
PWI
71.0
70
65
65.0
63.3
Normal
Mild
Moderate
60
0
1-2
3-4
5-6
7-8
9-10
11-12
Depression scores (DASS)
13-14
15-16
Conclusions
(a) 11-point end-defined scales are superior to
Likert scales
(b) Depression should be defined, and
measured, as a loss of positive affect.