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As the concept of quality of life (QOL) has evolved from a theoretical concept to both a measurable construct and an action-oriented change agent in the field of intellectual disabilities, there has emerged a corresponding need to develop, implement, and use a systematic approach to the assessment of domain-referenced quality of life outcomes. The purpose of this article is to suggest eight principles based on published literature and the authors' experiences that should underlie the assessment of QOL-related personal outcomes in the field of intellectual disabilities. Data from the development of the personal outcomes scale are used to exemplify each principle. The article's premise is that model development and test construction should work in tandem, and that a 'quality of life assessment instrument' should be based on an empirically derived QOL conceptual and measurement framework/model. [PUBLICATION ABSTRACT]
Soc Indic Res (2010) 98:6172 DOI 10.1007/s11205-009-9517-7
Accepted: 6 September 2009 / Published online: 29 September 2009 Springer Science+Business Media B.V. 2009
Abstract As the concept of quality of life (QOL) has evolved from a theoretical concept to both a measurable construct and an action-oriented change agent in the eld of intellectual disabilities, there has emerged a corresponding need to develop, implement, and use a systematic approach to the assessment of domain-referenced quality of life outcomes. The purpose of this article is to suggest eight principles based on published literature and the authors experiences that should underlie the assessment of QOL-related personal outcomes in the eld of intellectual disabilities. Data from the development of the personal outcomes scale are used to exemplify each principle. The articles premise is that model development and test construction should work in tandem, and that a quality of life assessment instrument should be based on an empirically derived QOL conceptual and measurement framework/model.
Keywords Quality of life Assessment
1 Introduction
During the 1980s and 1990s, the concept of quality of life (QOL) was primarily used in the eld of intellectual disability (ID) as a sensitizing notion that grounded and guided the initial efforts to understand its components and potential application. Before, people with ID were excluded from the mainstream of society (Schalock et al. 2007). Up until the
C. Claes (&) S. Vandevelde
Ghent University/University College, Ghent, Belgium e-mail: [email protected]
G. Van Hove J. van Loon
Ghent University, Ghent, Belgium
J. van Loon
Arduin Foundation, Middelburg, The Netherlands
R. L. Schalock
Hastings College, Hastings, NE, USA
Quality of Life Measurement in the Field of Intellectual Disabilities: Eight Principles for Assessing Qualityof Life-Related Personal Outcomes
Claudia Claes Geert Van Hove Jos van Loon Stijn Vandevelde Robert L. Schalock
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1970s and 1980s, quality of life was dened in terms of gains in adaptive behaviour skills or increases in scores on intelligence tests (Campo et al. 1997). The emergence of a broader concept of quality of life in the eld of intellectual disabilities had three primary sources: (a) a shift in focus away from the belief that scientic, medical, and technological advances alone would result in improved life towards an understanding that personal, family, community, and societal well-being emerge from complex combinations of these advances plus values, perceptions, and environmental conditions; (b) the next logical step from the normalization movement that stressed community-based services to measuring the outcomes from the individuals life to the community; and (c) the rise of consumer empowerment with its civil rights movements and its emphasis on person-centered planning, personal outcomes, and self-determination (Schalock et al. 2002, p. 457).
The quality of life concept is not new. Happiness and well-being were already discussed in ancient years by Plato and Aristotle (Schalock et al. 2007). The quality revolution of the 1980s had a broad impact on organizations accountability (stressing on outputs rather than inputs) and was inuenced by the positive psychology movement which ts attention to the identication and promotion of strengths and capacities of people and enhancing wellness (Schalock et al. 2007; Naidoo 2006). Throughout the literature, quality of life has been dened in many different ways, from general requirements for happiness (Prescott-Allen 2001) to positive life experiences (Campbell et al. 1976). Most researchers agree that social indicators as well as perceived well-being have to be brought into account when measuring quality of life, and that subjective and objective indicators are two complementary facets that need to be measured separately (Cummins 1997).
The construct of quality of life has been applied in the wider eld of health-related problems (drug-abuse, mental health, oncology, aging, cardiovascular diseases etc.), unfortunately with a relative lack of a theory-driven model or unied denition (Taillefer et al. 2003; Carr and Higginson 2001; Moon et al. 2006). Besides, many denitions start from professionals perspectives, while subjective preferences or experiences are ignored (Goode and Hogg 1994).
Also in the eld of ID, throughout the rst period the assessment of QOL was approached from multiple perspectives, resulting in over 1,243 measures reported in the QOL literature by the mid-1990s (Hughes et al. 1995). The current approach to the measurement of QOL can be characterized by: (a) its multidimensional nature involving core domains and indicators; (b) the use of methodological pluralism that includes the use of subjective and objective measures; (c) the incorporation of a systems perspective that captures the multiple environments impacting people at the micro, meso, and macrosystems levels; and (d) the increased involvement of persons with ID in the design and implementation processes (Bonham et al. 2004; Verdugo et al. 2005).
Although there is general consensus regarding these four measurement characteristics even quite common in the broader eld of social welfare studies (Inoguchi and Shin 2009)there are still two unresolved issues concerning the development of quality of life measures: the principles that should guide the measurement process and how QOL assessment should be undertaken (Cummins 2004; Perry and Felce 2002; Schalock et al. 2007). The purpose of the present article is to address these two issues by suggesting eight principles that should underlie the assessment of QOL-related personal outcomes. These eight principles are: (a) scale development should be based on a validated QOL conceptual and measurement framework; (b) a QOL-outcome measurement instrument has to be theory-based and inductively developed; (c) items measuring QOL-outcomes should be constructed in a methodologically sound way; (d) a QOL assessment instrument should
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Collect Items
Literature Expert -groups
Training in assessment
Pretest items
Internal consistency
Pilot version
Revised version
Accepted version
Pilot test
Principle 1-8 (see text)
Item analysis
Reliability Check
Validity Check
Final Form
Assessment
Training in assessment
Fig. 1 Guiding principles and used steps in the development process (based on Murphy and Davidshofer 1998)
address construct-related questions; (e) data-analysis and feedback should guide the developmental process; (f) correlation coefcients among respondents should be acceptable; (g) concurrent validity needs to be demonstrated; and (h) data should be collected in a conversation situation around the answers. These eight principles and their relationship to the assessment instruments developmental process are shown in Fig. 1. The eight developmental steps are based on the literature regarding psychological measurement scale development (Anastasi 1961; Cronbach and Meehl 1955; Murphy and Davidshofer 1998) and quality of life-assessment literature in the eld of ID (Brown et al. 2004; Cummins 1997; Schalock et al. 2008a, 2007).
This articles premise is that model development and test construction should work in tandem, and that a quality of life assessment instrument should be based on an empirically derived QOL conceptual and measurement framework/model that is: (a) formulated on the basis of observation, description and concept mapping; and (b) validated by demonstrating the factor structure of the models domains and determining the statistical characteristics of the domains and measurement indicators, including their etic (universal) and emic (culture-bound) properties. Furthermore, the assessment instrument should encompass a framework-related denition of quality of life. Throughout the work described in this article, the following denition of individual-referenced quality of life is used (Schalock et al. 2009):
Individual quality of life is a multi-dimensional phenomenon composed of core domains that are inuenced by personal characteristics and environmental variables.
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These core domains are the same for all people, although they may vary in relative value and importance. Quality of life domains are assessed on the basis of culturally sensitive indicators.
Throughout the article, the development and validation of the personal outcomes scale (POS; van Loon et al. 2008) will be used to exemplify each of the respective principles. The POS has been developed for the purpose of assessing quality of life of people with ID based on specic indicators associated with each of the eight core QOL domains that have been validated in a series of cross-cultural studies (Jenaro et al. 2005; Schalock et al. 2005; Schalock and Verdugo 2002; Wang et al. 2009). These eight domains are personal development and self determination (that reect a persons level of independence); interpersonal relations, social inclusion, and rights (that reect a persons social participation); and emotional, physical, and material well-being. The development of the instrument was guided by three signicant trends impacting the eld of intellectual disability: a quality of life measurement framework, assessing personal outcomes to enhance an individuals well-being, and using personal outcome information for multiple purposes including reporting and quality improvement.
1.1 Principle # 1: Scale Development Based on a Validated Conceptual and Measurement Framework
The concept of quality of life in the eld of ID has evolved from a sensitizing notion regarding what an individual values and desires, to a measurable construct and a framework guiding action-oriented changes in a multi-system perspective (Schalock et al. 2007). As a result of these changes, we are moving to the development of a more detailed and empirically based conceptual and measurement framework that is being used internationally for assessing personal outcomes, guiding organization and systems-level policies and practices, and implementing quality improvement strategies. Valid QOL-related instruments can contribute to the identication and evaluation of service delivery systems for people with ID (Perry and Felce 2002; Schalock et al. 2002), and increase our understanding of the etic and emic properties of the QOL construct.
In this regard, recent work in the conceptualization and measurement the QOL construct indicates that: (a) the QOL concept is characterized by its being multidimensional and hierarchical (Wang et al. 2009); (b) QOL factors and domains are more culture free, whereas QOL indicators are more cultural based (Jenaro et al. 2005; Schalock et al. 2005); and (c) particular aspects of personal well-being, as a measure of subjective well-being, may also show both etic and emic properties (Cummins 2005; Lau et al. 2005). The personal outcomes scale used as an exemplar in this article was based on these three ndings. The conceptual framework that guided the development of the POS is that the QOL concept is characterized by its being multidimensional, hierarchical, and has both etic (universal) and emic (culture-bound) properties. Table 1 summarizes these characteristics in terms of component (left column) and denition and examples (right column).
1.2 Principle # 2: A QOL-Outcome Measurement has to be Theory-Based and Inductively Developed
To ensure content validity, the development of the POS was based on participatory action research principles to ensure maximum relevance (Santelli et al. 1998). Specically, three processes reected this principle. First, the initial structure of the scale was based on the
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Table 1 Quality of life conceptual framework
Component Denition and examples
QOL factor Higher order construct (e.g., Independence, social participation, and well-being)
QOL domains Set of factors dening multidimensionality of QOL
Personal development & self-determination (independence)
Interpersonal relations, social inclusion, rights (social participation)
Emotional, physical, material well-being (well-being)
QOL indicators QOL-related perceptions, behaviors and conditions that dene operationally each QOL domain
Personal development: ADLs and IADLs
Self-determination: choices, decisions, control
Interpersonal relations: social networks friendships
Social inclusion: community integration/participation
Rights: human and legal
Emotional well-being: safety and security
Physical well-being: health and nutritional status
Material well-being: nancial status, employment
Indicator items Specic items used to assess personal outcomes on the basis of perceived well-being(self report) or an objective indicator of the persons life experiences and circumstances (direct observation)
eight core domains shown in Table 1, including multiple potential indicators based on those shown in the table. Second, expert judges in the eld of ID from Belgium, the Netherlands and the United States were asked to evaluate each potential item in reference to four criteria: (a) does the item reect what people want in their lives (importance); (b) does the item relate to current and future policy issues (relevance); (c) are the items assessed those that the service/supports provider has some control over (feasibility); and(d), can the ratings on the items be used for reporting and quality improvement purposes. Following a grounded theory approach to guarantee QOL-outcomes represent the perception of those who experience it, focus groups in Belgium (n = 10) and the Netherlands (n = 12) composed of important stakeholders (e.g., clients, families, direct support staff and professional experts) evaluated each potential item/indicator identied in reference to its value and importance to them (that is its cultural relevance/emic property). Based on this process, 124 items reecting the eight QOL domains became potential assessment items. Third, two parallel forms of a scale were developed for the measurement of both subjective and objective indicators resulting in a Self Report and a Direct Observation version. For comparability purposes, the content of each item was the same for the two versions. Descriptions were parallel on the two scales.
After receiving the input from the focus groups, the authors of the POS developed the parallel wording for the Self Report and Direct Observation versions. In addition, during this phase the authors nalized the 3-point rating scale for each item. A pilot version of the scale was administered in community based services and large facilities in Belgium and the Netherlands. Fourty advanced master students in Special Education were trained in how to administer the scale and how to take up the role of an interviewer. The training consisted of one theoretical session on QOL conceptual and measurement frameworks and administration procedures of the POS, followed by two practice sessions. Each potential interviewer administered the Scale to a partner student during a training session and observed
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the administration of the POS to a person with ID by a Master-trainer.1 For each interview, student-interviewers rated (using a 3-point likert scale) the instrument on the basis of: ease of presentation, administration, time required, clarity of the item to the person, level of understanding of the respondent, willingness of the respondent to provide the scores/ information, and clarity of the language used in the instrument. This information was used in the nal item-selection of the scale.
1.3 Principle # 3: Items Should be Constructed in a Methodologically Sound Way
Internal consistency and item discrimination are key psychometric properties required of an assessment instrument. To that end, and in reference to the development of the POS, Cronbachs alphas were calculated from the pilot study to determine internal consistency. The Scale was rened through these analyses, together with the feedback from the interviewers on the themesitems which were unclear are poorly described were deleted. Consequently, 28 indicator-items were removed from the Scale, resulting in 6 items per domain. These 6 items represented the highest alphas per domain.
A second pilot study was conducted in four facilities (three in the Netherlands and one in Belgium). Two Master Trainers administered the 6-items-per-domain-version of the Scale to 79 clients (or their proxies) who were interviewed by means of the Self-Report version. Additionally, this version of the Scale was also used for 79 staff members (or relatives) who completed the Direct Observation version on those 79 clients (54.4% male,45.6% female; age ranged from 18 to 79). These data were used to calculate Cronbach Alphas. The coefcients are shown in Table 2.
In addition to the above coefcients, Cronbach alpha coefcients were calculated within factor scores. In all cases (independence, social participation and well-being) these coefcients exceeded .70 for both the Self-Report and Direct Observation. Second, inter-correlations were computed between the eight QOL-domains and the total score for each version of the Scale. If the subscales do measure the same construct, coefcients are expected to be moderate or high, or about .4 to .9 (MacEachron 1982 cited in Thompson et al. 2002). Table 3 presents the inter-correlation coefcients for the Self Report version, and Table 4 for the Direct Observation version. As shown in Tables 3 and 4, all the reported coefcients are moderate or high (except Physical Well-being of the Direct Observation Form) and statistically signicant at the .01-level.
1.4 Principle # 4: Assessment Instruments Should Address Construct-Related Questions
A valid QOL assessment instrument should have the potential to address questions related to both the construct of QOL and intra-individual and between group differences in potential scores. For example, to determine whether or not the POS discriminates appropriately between groups, analyses of variance were computed using data from those 79 clients involved in the second pilot study. These potential differences were analyzed based on age, gender, and level of intellectual functioning (mild-moderate-severe-profound). The rationale used in the interpretation of these analyses is that there should be no differences in assessed QOL- scores between ages or gender, but that there should be signicant mean differences among the four levels of intellectual functioning. Based on these analyses,
1 Training interviewing degrees: Level 1: trained interviewer; Level 2: trainer interviewer (degree to train level 1-interviewer); Level 3: master trainer (degree to train level 2 interviewer).
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Table 2 Internal consistency coefcients (n = 79; CronbachAlphas)
Self-report Direct observation
Personal development .73 .65
Self-determination .72 .75
Interpersonal relations .72 .67
Social inclusion .81 .77
Rights .50 .40
Emotional well-being .70 .60
Physical well-being .68 .59
Material well-being .56 .44
Total .89 .86
Table 3 Inter-correlations of POS subscales and the total (n = 79): self report
PD SD IPR SI R EWB PHWB MWB
Total score .71** .67** .73** .69** .73** .59** .41** .54**
PD personal development; SD self-determination; IPR interpersonal relations; SI social inclusion; R rights; EMB emotional well-being; PHWB physical well-being; MWB material well-being
** p \ .01 (two-tailed)
Table 4 Inter-correlations of POS subscales and the total (n = 79): direct observation
PD SD IPR SI R EWB PHWB MWB
Total score .64** .71** .69** .72** .77** .57** .35** .59**
PD personal development; SD self-determination; IPR interpersonal relations; SI social inclusion; R rights; EMB emotional well-being; PHWB physical well-being; MWB material well-being
** p \ .01 (two-tailed)
there are no age or gender differences (F = 1.525 and .386, respectively; p [ .1) but there is a signicant difference among the four levels of intellectual functioning (F(3/76) = 11.6, p \ .00).
1.5 Principle # 5: Data-Analysis and Feedback Should Guide the Process of Development
The process of scale development is an interactive process of constructing, rening, analysing and rewriting. In the development of the POS, collected data provided feedback to rene the initial eld test into a nal form according to principle 3. This was a continuous process of observation, description, analyzing and concept-mapping. These processes are described in more detail in Schalock et al. (2009).
1.6 Principle # 6: Correlation Coefcients Between Respondents Should be Acceptable
Quality of life assessment requires rethinking the concept of reliability and its statistical determination. Rather than the traditional testretest reliability, for example, the inclusion
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of both self report and direct observation measures requires determining inter-rater reliability determinations, and the correlations between self report and direct observation measures. In reference to inter-rater reliability, three trained interviewers who were master students in the Department of Special Education at the Ghent University interviewed clients and respondents under the following two conditions: (a) clients (n = 50) and family members (n = 50) who acted as proxies were interviewed separately on the Self Report version; and (b) for each client, two staff members (n = 100) were interviewed on the Direct Observation version. Results are presented in Table 5 (n = 43 valid data). The guidelines of Cicchetti and Sparrow (Cicchetti 1994, p. 286; Cicchetti and Sparrow 1981; Tsatsanis et al. 2003) were used to evaluate these inter-rater reliability coefcients: .40 or lower = poor; .40.59 = fair; .60.74 = good; .75 or higher = excellent. As shown in Table 5, the POS inter-respondent reliability ranged from r = .29 (poor) to r = .79 (excellent). The POS Total Score inter-respondent reliability falls in the good to excellent range.
In reference to the correlation between self report and direct observation measures, data were collected during the second pilot study on 79 clients and 79 respondents (direct support staff or family members) to determine the correlation between the Self Report and Direct Observation versions of the Scale. These coefcients, which are all statistically signicant at the .01-level, are shown in Table 6.
Table 5 Inter-respondent reliability coefcients (n = 43)
* p \ .01
Domain Self report client versus proxy
Direct observation staff member 1 versus staff member 2
Personal development .57* .67*
Self-determination .47* .29
Interpersonal relations .68* .67*
Social inclusion .76* .78*
Rights .78* .76*
Emotional well-being .60* .69*
Physical well-being .45* .79*
Material well-being .55* .79*
Total .70* .78*
Table 6 Pearsons correlation coefcients between self report and direct observation versions of the POS (n = 79)
Domain Correlation between self-report and direct observation
Personal development .78*
Self-determination .72*
Interpersonal relations .52*
Social inclusion .74*
Rights .80*
Emotional well-being .42*
Physical well-being .63*
Material well-being .71*
Total .83*
* p \ .01
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1.7 Principle # 7: Concurrent Validity Needs to be Demonstrated
Concurrent validity is the extent to which a persons score on a certain test (in this case the POS) correlates with a criterion measure, which is usually that persons score on another test (in this case the GENCAT-Scale; Verdugo et al. 2008). We approached the demonstration of concurrent validity through the administration of the Direct Observation version of the POS and the GENCAT (which is based on objective measures of QOL-indicators only). In this study the POS was administered by a trained interviewer using the Directions for Direct Observation Version. The GENCAT was completed by a respondent under the direction of the same trained interviewer, who initially explained the purpose of the study and gave a brief overview of the GENCAT (n = 58). During the respondents completion of the GENCAT, the interviewer was available for clarifying any items and answering any questions from the respondents. These concurrent validity coefcients are presented in Table 7.
1.8 Principle # 8: Data Should be Collected in a Conversation Format
Data should be collected in a conversation setting/format that is structured around the items. What this amounts to is that the interviewer is engaged in a conversation with the respondent, including describing and discussing the specic item with the respondent. The interviewer does not simply read the item to the person or simply ask the person to respond to the item. In addition, in the administration procedures of the POS, strong emphasis is made on the interviewer to be familiar with the QOL-framework and to be trained in interviewing techniques. The interviewer is supposed to clarify the intent of the assessment precisely and has to guarantee the scale had not been developed to evaluate the persons ability or that the data will be used to classify the person or affect the persons eligibility for services and supports. In making clear the purpose of the interview, the interviewer should give assurance that a QOL assessment scale is not a test with right or wrong answers.
2 Discussion
The present article uses the development and validation of a QOL personal outcomes scale in the eld of ID to discuss eight psychological measurement principles applicable to the development of subsequent quality of life assessment instruments. The described QOL
Table 7 Pearsons correlation coefcients between direct observation version of the POS and the GENCAT (n = 58)
* p \ .01
Domain Correlation between direct observation POS and GENCAT
Personal development .61*
Self-determination .79*
Interpersonal relations .57*
Social inclusion .37*
Rights .47*
Emotional well-being .55*
Physical well-being .65*
Material well-being .23
Total .87*
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assessment procedure corresponds with four key-notions, i.e., utility, robustness, understanding and relevance.
2.1 Utility
The POS provides information that can be used for quality improvement and evidence-based practices (Schalock et al. 2008a, b). On the individual level, the POS can be used to:(a) provide feedback to the person regarding his/her status on the eight domains composing a life of quality, and whether or not personal and organizational-level quality improvement strategies have made a difference in the persons life; (b) establish an expectation that change is possible and can occur in the multiple dimensions composing a life of quality; (c) conrm that the organization serving the client is committed to a holistic approach to the person; and (d) compare subjective and objective assessments of quality of life indicators. On the organizational level, POS-data can be used to: (a) share information about client outcomes and changes in those outcomes over time (Self Evaluation); (b) determine which individual, organization-referenced, and community factors predict outcome scores (Evidence-Based Practices); and (c) use information about outcomes and their signicant predictors as a basis for data tutorials, right to left thinking, and targeting signicant predictor variables. At the macro-level, measuring personal outcomes provides information for public policy in terms of funding mechanism and managing for results.
2.2 Robustness
Since the POS may provide information on a wide range of issues improving QOL, the quality of the collected data is essential through the demonstration of reliability and validity. The assessment of the POS includes both subjective/self-report and objective/ direct observation ratings. Consistency between self-report and direct-observation data suggests that the POS can serve a useful role in using proxies when the person cannot be the primary respondent. During the development of the scale special attention was given to training procedures, since the POS requires administration skills that are different from traditional assessment methodology that is used in the eld (e.g., the assessment of adaptive behaviour with items on communication, daily living skills or socialisation). Without training, interviewers may be not familiar with quality of life related principles and the importance of collecting information in an interview format.
2.3 Understanding
In a QOL-interview, both the interviewer and the respondent must clearly understand the meaning of the items. A conversation style should focus on the person being interviewed and training procedures should focus on clearly understood item-descriptions, understanding and respondent encouragement, and the use of augmentative or alternative communication if necessary.
2.4 Relevance
The concept of QOL has numerous possible indicators. In respect to its etic (universal) and emic (culture-bound) properties, the items selection should be based on available literature and cross-cultural studies (domains) and modied on focus-groups (indicators). In that
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regard, information presented in this article indicates that the POS is theory-based and inductively developed by active involvement of signicant participants in focus groups. Internal consistency is acceptable, even though each domain consists of only six items. The low Cronbach Alphas for the subdomains rights and material well-being might suggest those domains are most inuenced by subjective factors. Inter-correlation between the subscales and the total score are good, indicating that the subdomains provide similar, but not identical types of information. Inter-respondent reliability is acceptable. Concurrent validity was established by showing signicant correlations between the POS and the GENCAT, a similar instrument measuring personal outcomes. In summary, the POS has satisfactory psychometric properties and therefore can be used with condence in research and evaluation activities.
In conclusion, the suggested principles that guided the development process of the personal outcomes scale emphasize the importance of an empirically derived QOL conceptual and measurement framework and underscore the unique procedures of how QOL assessment should be undertaken in order to address the four key-notions mentioned in this paper, i.e., utility, robustness, understanding and relevance.
Although developed in the eld of ID, to the authors opinion the eight principles together with the four measurement characteristics (multidimensionality, subjective and objective measures, systems perspective and involvement of the persons) suggested in this article can support any attempt of measuring quality of life related personal outcomes in the broader eld of health and social welfare studies.
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