Problems of transforming scales of life satisfaction

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Problems of transforming
scales of life satisfaction
Euromodule workshop
Berlin, 18-19 October 2002
Sergiu Bălţătescu
University of Oradea
Life satisfaction

Defined as an overall, cognitive evaluation of
one's life.
 A construct generally measured by single direct
questions
 Single scales: two formulation of the questions:
– referring to the 'satisfaction with the life one leads’
– referring to 'satisfaction with life-as-a-whole’

Scales with 3, 4, 5 points
– with answer categories verbally labeled

Scales with 10, 11 and 101 points
– represented on a pseudo-graphic scales,
– only the extreme values are represented verbally.
(Veenhoven, 1993)
Why we need knowledge about
the transformation of life
satisfaction scales ?

PRACTICAL REASONS: To homogenize life
satisfaction data, in order to compare levels of
subjective well-being:
– between nations
– through time
Examples:
- compare national life satisfaction means of Euromodule
and non-Euromodule countries
– make compatible the time-trend of life satisfaction
obtained with another survey program (Diagnosis of
quality of life 1990-1999) with Euromodule Romania
(2003? -
Why we need knowledge about
the transformation of life
satisfaction scales ?

THEORETICAL REASONS:
– Assess the convergent validity of new measures
• Example: results from new international programs (like
Euromodule) can be compared with the results of other
national surveys which are using different life satisfaction
scales.
– Analyze through conversion some characteristics of life
satisfaction scale used.
• Example: which level of measurement can be assessed to
life satisfaction scale we use - ordinal or interval ?
The initial scale


Used in ‘Diagnosis of quality of life’ survey
program (ICCV, 1990-1999) (for the analysis was
used the 1999 data set)
Sample: national, random, around 1200 cases
A 5-point simple life satisfaction scale:
“Considering the whole situation, how satisfied are you about your
daily life?
a. Very unsatisfied
b.Unsatisfied
c.Neither unsatisfied, nor satisfied
d.Satisfied
e.Very satisfied”
See: Mărginean (1991), Zamfir (1992)
See also: www.iccv.ro
Distribution of the initial variable
(Diagnosis of Quality of life 1999)
35,00%
33,30%
31%



Mean: 2,71 (under
the mean value of
the scale)
Slightly positively
skewed
See next the
graphic
representation of
the distribution
30,00%
25,00%
23,40%
20,00%
15,00%
10,80%
10,00%
5,00%
1,30%
0,00%
very unsatisfied
unsatisfied
neither unsatisfied nor
satisfied
satisfied
very satisfied
The target scale




11-point pseudo-interval
scale
Only the extremes are
represented verbally
Has graphic elements
Used in the Euromodule
questionnaire
See: Delhey, J.,
P. Bohnke, et al. (2002).
Goals for transforming life
satisfaction scales

A. Convert an ordinal scale into another
– Ex: a 5-step life satisfaction scale into an
11-step life satisfaction scale

B. Assigning interval values to an ordinal
scale
– Ex: assign scores for each answers on a
5-step life satisfaction scale, and assess
the true (empirical) distance between the
categories

C. Combining the two approaches
Methods for converting an ordinal
scale into another

1. Linear (conventional) transformation
– the simplest way to convert scales, using an
unique formula
– used implicitly for homogenizing means of life
satisfaction scales in World Database of
Happiness (Veenhoven, 1993)

2. Transformation by expert ratings
– the analyst, a panel of expert researchers or
typical respondents are assigning to each
category of the original scale a value (or
category) on the target variable
• Ex: very unsatisfied-3, somehow satisfied 6, very satisfied - 9
Linear (conventional)
transformation
Formula used for converting into a 11 point scale
Ai - A0
Bi = ___________ x 10
An - A0
where
Bi = Transformed value (to 11-point scale)
Ai = Value on original scale
A0 = Lowest possible score on original scale
An = Highest possible score on original scale (Veenhoven,
1993)
Examples:
For a 5-point Likert scale (assumed with equal intervals, with values from 1 to
5), the transformed values are: 0, 2.5, 5, 7.5, 10
Proprieties:
a.
formula is designed in such a way that the end-points of the original
scale coincide after transformation with the endpoints of the target (010) scale.
b.
while stretching the scale, the linear transformation preserves the initial
distances between the values. That is why it can be used also for
transforming scales whose categories are at non-equal distances. See
later how useful can be this feature.
Ratings of typical respondents
Typical respondents: Sample of
students from the University of
Oradea (N=116)
–
–
–
Specialization: Sociology,
Social work
Sex: Males 14 %, Females: 86 %
Age mean: 22
They were asked to rate the
categories of the 5-step life
satisfaction scale:
a. On a graphic scale (10 cm. long).
The distance of the signs to the left
extremity was measured in cm.
b. On a pseudo-interval scale (with graphic
elements), as used in the
Euromodule questionnaire
See right the original questionnaire,
in Romanian language
1. În ce loc, pe scala de mai jos, s-ar afla cineva care dă unul din cele 5 răspunsuri la
următoarea întrebare? Puneţi câte un x pe scală, acolo unde credeţi că ar corespunde cele
5 răspunsuri.
LUÂND ÎN CONSIDERARE ÎNTREAGA SITUATIE, CÂT DE MULŢUMIT
SUNTETI DE VIATA DVS. DE ZI CU ZI ?
Foarte nemulţumit
Nemulţumit
Nici nemulţumit, nici mulţumit
Mulţumit
Foarte mulţumit
Total nemulţumit
de viaţa de zi cu zi
Total mulţumit
de viaţa de zi cu zi
2. La ce număr, pe scara de mai jos, s-ar afla cineva care dă unul din cele 5 răspunsuri la
următoarea întrebare? Încercuiţi numărul din dreptul scalei care i s-ar potrivi cel mai
bine:
LUÂND ÎN CONSIDERARE ÎNTREAGA SITUATIE, CÂT DE MULŢUMIT
SUNTETI DE VIATA DVS. DE ZI CU ZI ?
Total mulţumit
Foarte mulţumit
Mulţumit
Nici nemulţumit, nici mulţumit
Nemulţumit
Foarte nemulţumit
Total nemulţumit




Means of the ratings have been
calculated and plotted (line from
every point to centroid point and
regression line included)
8 outliers (7% of ratings excluded
from the analysis)
The resulted correlation between
the mean of ratings on the two
scales is high (r = 0.72)
Mean ratings on pseudo-interval
scale was higher m(Xp)=5.19
m(Xg)=4.94

The assigned values for the
categories were calculated as the
mean of ratings of each category
 The resulted ratings:
Xp=(0.8; 2.440; 4.628; 6.973; 9.098) on the pseudo-interval scale
Xs=(1.16; 2.94; 5.03; 7.15; 9.00) on the graphic scale
means of estimations on the peudo-interval scale
Ratings of the typical respondents

8,00
m ean_s = 2.01 + 0.64 * m ean_l
R-Square = 0.52

7,00





6,00


 
      

    
  
 
  
  

  
 
   
5,00

4,00





3,00

2,00
3,00
4,00
5,00
6,00
Linear Regression
7,00
means of estimations on the graphic scale
Assigning interval values to an
ordinal scale
1.
2.
Estimation from the observed
frequencies and distributional
assumption
Optimal scoring
Estimation from the observed frequencies and
distributional assumption
Used when researchers assumes that the latent variable
has a particular distribution (ex: rectangular, normal) We
can consider that observed categories correspond to
separate segments under the density function of the
latent variables
For normal curve, we use a table of areas under the normal
curve to estimate the upper & lower boundaries of each
segment under the density function.
After that, we calculate (or use a table of) the ordinates of
the normal curve for the upper and lower boundaries.
We substract the valueas and divides the results by a
propostion of this category

See: Hensler & Stipak (1979)
Computing of the estimation from the observed
frequencies and distributional assumption
10,8%
33.4%
x1
x2
z1
23.4%
31,0%
x3
z2
1,3%
x4
z3
x5
z4
Z values corresponding areas under the normal curve
(-1,61; -0,77; 1,16; 2,49)
Ordinates on the normal curve of Z values
f(Z)=(0,1092; 0,2966; 0,2036; 0,018)
Values of estimates calculated by subtracting ordinate of the lower boundary from the
ordinate of the upper boundary and dividing by the proportion of each category
xj=(-1,01111; -0,56276; 0,3; 0,793162; 1,384615)
Scores linearly transformed to 0-10 scale
(0; 1,87145; 5,472708; 7,531217; 10)
The optimal scoring method (OSM)





The algorithm is rather new (Young et al., 1981).
Precursors: Cattell (1962), Allen (1976), Hensler &
Stipak (1979)
OSM begins with the premise that the problem of
obtaining latent interval scores for ordinal variables is
inherently insoluble.
Thus, we should use scoring systems which
maximally simplify the empirical relationship within a
set of variable. "Specifically, optimal scores are those
which maximize the average inter-item correlation
within a set of variables." (Allen, 1976)
The problem looks similar to that of maximizing the
internal consistency of a set of variables. (calculating
the Crombach -  coefficient)
Regression with optimal scaling






Is a version of the optimal scoring method
Implemented in SPSS (CATREG algorithm)
See Nichols (1995)
Represents a variant of linear regression in which the
scores for the variables are not given before, but calculated
after, in such a way that assures the best fit of the model
(maximizing r square)
Practically, it stretches the measurement scales of the
variables, assigning scores for their categories, to obtain a
maximal fitness of the linear regression model, the only
constraint being that of the monotonicity of variables.
Allows the theoretical model to prevail: if the researcher
assumes that one of the variables is interval-level, this
variable will be entered in the model as such, and its values
will not be changed
Used recently for analyzing life satisfaction data (Shen &
Lai, 1998)
Regression with optimal scaling as a method
for transforming life satisfaction scales





Source data: Diagnosis of quality of life survey program
(ICCV, 1990-1999) (for the analysis was used the 1999 data set)
Sample: national, random, 1198 cases
Dependent variable: life satisfaction
Independent variables: 19 domain satisfaction indicators
(ex: satisfaction with family, with the political situation,
neighborhood, etc.)
Theoretical model: bottom-up
Results: The goodness of fit (r square) increases from 0,34 to 0,38
 New scores were assigned to life satisfaction indicator categories:

(-1,827; -0,665; 0,186; 1,221; 3,729)
Scores linearly transformed to 0-10 scale
(0;
2,091; 3,623; 5,485; 10)
Quantification of life satisfaction
(By CATREG algorithm)
The algorithm dramatically
increases the distance between
scores assigned to “satisfied”
and “very unsatisfied”
categories - to about a half of
the amplitude on the target
scale (see figure) As a result,
the computed mean on 0-11
scale is lower than the means
calculated by other methods
(see next slide)
Possible interpretation: it is very
hard (or unusual) to be very
satisfied in Romania
Indeed, the percent of those who
declared themselves being very
satisfied is about 1,3 %
Transformation results
neither
very
unsatisfied
very
unsatisfied
satisfied
unsatisfied
nor
satisfied
satisfied
Linear calculation (equalinterval 0-10 scale)
Equal-interval 1-9 scale
Expert rating-graphic scale
Expert rating - pseudo-interval
scale
Values calculatted assuming
normal distribution
Quantification by regression
with optimal scaling
Mean
0
2,5
5
7,5
10
4,27
1
0,8
3
2,4
5
4,6
7
7,0
9
9,1
4,41
4,08
1,2
2,9
5,0
7,1
9
4,45
0
1,9
5,5
7,5
10
4,21
0
2,1
3,6
5,5
10
3,23
Evaluation of the methods:
linear transformation



Preserves the ratio of initial distances between categories
Can be used to transform values assigned to rank-order
categories
May cause problems because is thus designed that the
end-point of the original scale coincide after transformation
to the end-points of the target (0-10) scale, when in fact:
– The panel of typical respondents assigned the end-points to 1
and 9
– In the surveys using 0-10 scales, the extreme categories are in
very few cases chosen

It might be recommended to transform values to 1-9 scale,
and use scores as if they are on a 0-10 scale
Evaluation of the methods:
rating by experts

Is more complicated to use: we need a
separate research to asses the value
 The ratings tend to be close to the equalinterval assigning on a 0-9 scale (1,3,5,7,9)
 It is recommended to be used for recent
data (we cannot be sure the meaning of
categories of life satisfaction is not
changing in time)
Evaluation of the methods:
estimation from the observed frequencies and
distributional assumption



We cannot always assumes a normal distribution
of the life satisfaction variable
This works in the case of Romania 1990-1999,
where the distribution is close to normal
In western European countries, life satisfaction
scores are markedly positively skewed
(Cummins, 1998)
Evaluation of the methods:
regression with optimal scaling




The value is very dissimilar with the other
calculations (in our sample)
The calculated optimal scores may differ from a
sample to another, as the structure of subjective
well being differs
There is no guarantee that the final scoring
reflects the true measurement level of the
dependent variable, or the functional relationship
between variables
The method is rather new and deserves further
tests
Limitations





The analysis is not exhaustive. Several methods like linear
testing both scales in the same sample (recommended by
Veenhoven) maximin (Abelson & Tukey), psycholinguistic
estimation, estimation from criterion variables (Hensler &
Spiwak) and other variants of optimal scaling were omitted
The number of predictors in regression with optimal scaling
was rather small.
A closer attention must be given to missing data analysis
The issue of transformation of the scales with or not with
central points was omitted
There was no attention given to the semantic difference of
terms between languages
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