Dataset Information

Questionnaire discrimination: (re)-introducing coefficient delta.

ABSTRACT:

Background

Questionnaires are used routinely in clinical research to measure health status and quality of life. Questionnaire measurements are traditionally formally assessed by indices of reliability (the degree of measurement error) and validity (the extent to which the questionnaire measures what it is supposed to measure). Neither of these indices assesses the degree to which the questionnaire is able to discriminate between individuals, an important aspect of measurement. This paper introduces and extends an existing index of a questionnaire's ability to distinguish between individuals, that is, the questionnaire's discrimination.

Methods

Ferguson (1949) 1 derived an index of test discrimination, coefficient delta, for psychometric tests with dichotomous (correct/incorrect) items. In this paper a general form of the formula, deltaG, is derived for the more general class of questionnaires allowing for several response choices. The calculation and characteristics of deltaG are then demonstrated using questionnaire data (GHQ-12) from 2003-2004 British Household Panel Survey (N = 14761). Coefficients for reliability (alpha) and discrimination (deltaG) are computed for two commonly-used GHQ-12 coding methods: dichotomous coding and four-point Likert-type coding.

Results

Both scoring methods were reliable (alpha > 0.88). However, deltaG was substantially lower (0.73) for the dichotomous coding of the GHQ-12 than for the Likert-type method (deltaG = 0.96), indicating that the dichotomous coding, although reliable, failed to discriminate between individuals.

Conclusion

Coefficient deltaG was shown to have decisive utility in distinguishing between the cross-sectional discrimination of two equally reliable scoring methods. Ferguson's delta has been neglected in discussions of questionnaire design and performance, perhaps because it has not been implemented in software and was restricted to questionnaires with dichotomous items, which are rare in health care research. It is suggested that the more general formula introduced here is reported as deltaG, to avoid the implication that items are dichotomously coded.

SUBMITTER: Hankins M

PROVIDER: S-EPMC1884165 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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Questionnaire discrimination: (re)-introducing coefficient delta.

Hankins Matthew M

BMC medical research methodology 20070518

<h4>Background</h4>Questionnaires are used routinely in clinical research to measure health status and quality of life. Questionnaire measurements are traditionally formally assessed by indices of reliability (the degree of measurement error) and validity (the extent to which the questionnaire measures what it is supposed to measure). Neither of these indices assesses the degree to which the questionnaire is able to discriminate between individuals, an important aspect of measurement. This paper ...[more]

PMID: 17511862

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Project description:BackgroundThe anticipation of mental health-related discrimination is common amongst people with mental health problems and can have serious adverse effects. This study aimed to develop and validate a measure assessing the extent to which people with mental health problems anticipate that they will personally experience discrimination across a range of contexts.MethodsThe items and format for the Questionnaire on Anticipated Discrimination (QUAD) were developed from previous versions of the Discrimination and Stigma Scale (DISC), focus groups and cognitive debriefing interviews which were used to further refine the content and format. The resulting provisional version of the QUAD was completed by 117 service users in an online survey and reliability, validity, precision and acceptability were assessed. A final version of the scale was agreed and analyses re-run using the online survey data and data from an independent sample to report the psychometric properties of the finalised scale.ResultsThe provisional version of the QUAD had 17 items, good internal consistency (alpha = 0.86) and adequate convergent validity as supported by the significant positive correlations with the Stigma Scale (SS) (r = 0.40, p < 0.001) and the Internalised Stigma of Mental Illness Scale (ISMI) (r = 0.40, p < 0.001). Three items were removed due to low endorsements, high inter-correlation or conceptual concerns. The finalised 14 item QUAD had good internal consistency (alpha = 0.86), good test re-test reliability (?(c) = 0.81) and adequate convergent validity: correlations with the ISMI (r = 0.45, p < 0.001) and with the SS (r = 0.39, p < 0.001). Reading ease scores indicated good acceptability for general adult populations. Cross-replication in an independent sample further indicated good internal consistency (alpha = 0.88), adequate convergent validity and revealed two factors summarised by institutions/services and interpersonal/professional relationships.ConclusionsThe QUAD expanded upon previous versions of the DISC. It is a reliable, valid and acceptable measure which can be used to identify key life areas in which people may personally anticipate discrimination, and an overall tendency to anticipate discrimination. It may also be useful in planning interventions aimed at reducing the stigma of mental illness.

Project description:Stable isotope analysis of diet has become a common tool in conservation research. However, the multiple sources of uncertainty inherent in this analysis framework involve consequences that have not been thoroughly addressed. Uncertainty arises from the choice of trophic discrimination factors, and for Bayesian stable isotope mixing models (SIMMs), the specification of prior information; the combined effect of these aspects has not been explicitly tested. We used a captive feeding study of gray wolves (Canis lupus) to determine the first experimentally-derived trophic discrimination factors of C and N for this large carnivore of broad conservation interest. Using the estimated diet in our controlled system and data from a published study on wild wolves and their prey in Montana, USA, we then investigated the simultaneous effect of discrimination factors and prior information on diet reconstruction with Bayesian SIMMs. Discrimination factors for gray wolves and their prey were 1.97‰ for δ13C and 3.04‰ for δ15N. Specifying wolf discrimination factors, as opposed to the commonly used red fox (Vulpes vulpes) factors, made little practical difference to estimates of wolf diet, but prior information had a strong effect on bias, precision, and accuracy of posterior estimates. Without specifying prior information in our Bayesian SIMM, it was not possible to produce SIMM posteriors statistically similar to the estimated diet in our controlled study or the diet of wild wolves. Our study demonstrates the critical effect of prior information on estimates of animal diets using Bayesian SIMMs, and suggests species-specific trophic discrimination factors are of secondary importance. When using stable isotope analysis to inform conservation decisions researchers should understand the limits of their data. It may be difficult to obtain useful information from SIMMs if informative priors are omitted and species-specific discrimination factors are unavailable.

Project description:ObjectiveIn 2009, in a European survey, around a quarter of Europeans reported witnessing discrimination or harassment at their workplace. The parity committee from the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) designed a questionnaire survey to investigate forms of discrimination with respect to country, gender and ethnicity among medical professionals in hospitals and universities carrying out activities in the clinical microbiology (CM) and infectious diseases (ID) fields.DesignThe survey consisted of 61 questions divided into five areas (sociodemographic, professional census and environment, leadership and generic) and ran anonymously for nearly 3 months on the ESCMID website.SubjectsEuropean specialists in CM/ID.ResultsOverall, we included 1274 professionals. The majority of respondents (68%) stated that discrimination is present in medical science. A quarter of them reported personal experience with discrimination, mainly associated with gender and geographic region. Specialists from South-Western Europe experienced events at a much higher rate (37%) than other European regions. The proportion of women among full professor was on average 46% in CM and 26% in ID. Participation in high-level decision-making committees was significantly (>10 percentage points) different by gender and geographic origin. Yearly gross salary among CM/ID professionals was significantly different among European countries and by gender, within the same country. More than one-third of respondents (38%) stated that international societies in CM/ID have an imbalance as for committee member distribution and speakers at international conferences.ConclusionsA quarter of CM/ID specialists experienced career and research discrimination in European hospitals and universities, mainly related to gender and geographic origin. Implementing proactive policies to tackle discrimination and improve representativeness and balance in career among CM/ID professionals in Europe is urgently needed.

Dataset Information

Questionnaire discrimination: (re)-introducing coefficient delta.

Background

Methods

Results

Conclusion

Publications

Questionnaire discrimination: (re)-introducing coefficient delta.

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