What is the relationship between the minimally important difference and health state utility values? The case of the SF-6D

BACKGROUND: The SF-6D is a new single summary preference-based measure of health derived from the SF-36. Empirical work is required to determine what is the smallest change in SF-6D scores that can be regarded as important and meaningful for health professionals, patients and other stakeholders. OBJECTIVES: To use anchor-based methods to determine the minimally important difference (MID) for the SF-6D for various datasets. METHODS: All responders to the original SF-36 questionnaire can be assigned an SF-6D score provided the 11 items used in the SF-6D have been completed. The SF-6D can be regarded as a continuous outcome scored on a 0.29 to 1.00 scale, with 1.00 indicating "full health". Anchor-based methods examine the relationship between an health-related quality of life (HRQoL) measure and an independent measure (or anchor) to elucidate the meaning of a particular degree of change. One anchor-based approach uses an estimate of the MID, the difference in the QoL scale corresponding to a self-reported small but important change on a global scale. Patients were followed for a period of time, then asked, using question 2 of the SF-36 as our global rating scale, (which is not part of the SF-6D), if there general health is much better (5), somewhat better (4), stayed the same (3), somewhat worse (2) or much worse (1) compared to the last time they were assessed. We considered patients whose global rating score was 4 or 2 as having experienced some change equivalent to the MID. In patients who reported a worsening of health (global change of 1 or 2) the sign of the change in the SF-6D score was reversed (i.e. multiplied by minus one). The MID was then taken as the mean change on the SF-6D scale of the patients who scored (2 or 4). RESULTS: This paper describes the MID for the SF-6D from seven longitudinal studies that had previously used the SF-36. CONCLUSIONS: From the seven reviewed studies (with nine patient groups) the MID for the SF-6D ranged from 0.010 to 0.048, with a weighted mean estimate of 0.033 (95% CI: 0.029 to 0.037). The corresponding Standardised Response Means (SRMs) ranged from 0.11 to 0.48, with a mean of 0.30 and were mainly in the "small to moderate" range using Cohen's criteria, supporting the MID results. Using the half-standard deviation (of change) approach the mean effect size was 0.051 (range 0.033 to 0.066). Further empirical work is required to see whether or not this holds true for other patient groups and populations

Sample size and power estimation for studies with health related quality of life outcomes: a comparison of four methods using the SF-36

We describe and compare four different methods for estimating sample size and power, when the primary outcome of the study is a Health Related Quality of Life (HRQoL) measure. These methods are: 1. assuming a Normal distribution and comparing two means; 2. using a non-parametric method; 3. Whitehead's method based on the proportional odds model; 4. the bootstrap. We illustrate the various methods, using data from the SF-36. For simplicity this paper deals with studies designed to compare the effectiveness (or superiority) of a new treatment compared to a standard treatment at a single point in time. The results show that if the HRQoL outcome has a limited number of discrete values (< 7) and/or the expected proportion of cases at the boundaries is high (scoring 0 or 100), then we would recommend using Whitehead's method (Method 3). Alternatively, if the HRQoL outcome has a large number of distinct values and the proportion at the boundaries is low, then we would recommend using Method 1. If a pilot or historical dataset is readily available (to estimate the shape of the distribution) then bootstrap simulation (Method 4) based on this data will provide a more accurate and reliable sample size estimate than conventional methods (Methods 1, 2, or 3). In the absence of a reliable pilot set, bootstrapping is not appropriate and conventional methods of sample size estimation or simulation will need to be used. Fortunately, with the increasing use of HRQoL outcomes in research, historical datasets are becoming more readily available. Strictly speaking, our results and conclusions only apply to the SF-36 outcome measure. Further empirical work is required to see whether these results hold true for other HRQoL outcomes. However, the SF-36 has many features in common with other HRQoL outcomes: multi-dimensional, ordinal or discrete response categories with upper and lower bounds, and skewed distributions, so therefore, we believe these results and conclusions using the SF-36 will be appropriate for other HRQoL measures

Physical activity, weight status and diet in adolescents: are children meeting the guidelines?

Childhood obesity is on the increase and maintaining regular physical activity and consuming a healthy diet have become essential tools to combat the condition. The United Kingdom government has recommended guidelines for optimal levels of diet and activity in children. The aim of this paper is to describe and compare self-reported physical activity levels, diet, and Body Mass Indices (BMI) amongst adolescent children, aged 11-15, in the South West (SW) and North West (NW) regions of England and to see if these children were meeting the current targets for optimal levels of: physical activity; fruit/vegetable consumption; fat consumption and BMI. We report the results of a cross-sectional survey of four secondary schools and 1,869 children using the self-reported Western Australian Child and Adolescent Physical Activity and Nutrition Survey (CAPANS) physical activity instrument and a food intake screener questionnaire, in summer and winter. We found that 25% (469/1869) 95% CI: 23% to 27%, of children engaged in 60 minutes of moderate to vigorous physical activity per day; 53% (995/1866) 95% CI: 51% to 56%, took 5 portions of fruit and vegetables per day; while 22% (407/1861) 95% CI: 20% to 24% consumed recommended amount of fats, and 23.7% (276/1164) 95% CI: 21% to 26%, of pupils were obese or overweight as classified by their BMI. Self reported physical activity in young people regardless of area is lower than previously reported and the lack of students engaging in 60 minutes moderate to vigorous activity could have serious public health consequences. If sustained, this could lead to more overweight adults, and more ill health

Physical activity among adolescents and barriers to delivering physical education in Cornwall and Lancashire, UK: a qualitative study of heads of PE and heads of schools. BMC Public Health Journal 2008 Aug 1;8:273.

BACKGROUND: Recent initiatives have been introduced by the UK government into secondary schools to increase pupils' access to physical activity (PA). Despite this, not enough is known about pupils' levels of physical activity or whether the delivery of these initiatives in schools facilitates or creates a barrier for pupils' PA. The aim of this study was to gain an understanding of adolescents PA levels from the perspective of those responsible for delivering physical education (PE) in schools; heads of PE (HOPE) and heads of school (HS). METHODS: Seventeen semi-structured qualitative interviews were carried out with a snowball sample of HOPE and HS in schools in the Northwest and Southwest of England. Thematic data analysis using NVIVO was used to identify emergent themes.RESULTS:17 core themes were generated, 12 of which confirmed the findings from similar research. However, five themes relating to 'ethos of performance/elitism', 'lower fitness leads to lower ability', 'undervaluing activities within PE dept' or school as a whole', 'role of the school' and 'PE department doing all it can' offer valuable new insight into the factors which may encourage or prevent PA inside or outside the curriculum. CONCLUSION: Despite many positive perceptions of the delivery of PE in schools, it is evident that barriers still exist within that delivery which discourages physical activity. More research is needed to particularly address the complex issues of elitism and the ethos of PA in schools

Testing Fair Wage Theory

Fairness considerations often are invoked to explain wage differences that appear unrelated to worker characteristics or job conditions, but non-experimental tests of fair wage models are rare and weak because of the limits of available market-generated data. In particular, such data rarely permit researchers to (a) identify suitable reference points that employees and employers might use in determining what is fair and (b) control for employees’ marginal output and its value. This study utilizes a unique dataset from the baseball labor market that solves both problems. We find no support for fair wage theory in this market. We also find that fairness premia can be illusory: Wages appear to be adjusted upward for reasons of fairness in regressions that control for variation in individuals’ physical output, but such premia evaporate when the value of that output (which can be market- or firm-specific) is held constant. This suggests that avoiding proxy measures of workers’ marginal revenue products in wage studies might reduce the number of labor market "anomalies" economists must resolve.fairness, efficiency wages, wage differentials

The Existence and Persistence of a Winner’s Curse: New Evidence from the (Baseball) Field

This study takes advantage of recent developments in the measurement and valuation of individual output in the baseball labor market to (i) reassess prior evidence that this market is afflicted by the winner’s curse phenomenon and (ii) test whether bidders learn to avoid this curse over time. Though we find no evidence of negative average returns on player contracts for the earliest cohort of baseball free agents, we conclude that teams in that era failed to efficiently discount their bids in accord with available information, especially about risk. What is more, evidence from a larger sample of players signed in the late 1990s shows that teams have continued to overvalue inconsistent free agents and failed to limit their bids to conform to players’ lower values in small markets. This is consistent with experimental evidence that finds bounded-rational behavior when bidders are faced with complex valuation problems involving multiple elements.market efficiency, bounded rationality, overbidding

Growth, Research & Development, and Uncertainty: An Empirical Analysis in Finland

Invention and innovation are the most important aspects in the growth and development of a country. Investors come up with innovative ideas that can play a role in the development of technology in the country. The research and development (R&amp;D) sector is very much associated with this, as it comprises researchers who have the ability to think creatively and come up with innovative ideas and designs for firms. It can be stated that countries where the research sector is well-developed and well-maintained have a greater chance to enjoy better economic growth (EG). The core purpose of the current study is to understand the influence of R&amp;D and uncertainties associated with R&amp;D on the EG of Finland. Based on this context, the researcher has gathered data on relative variables in Finland for 29 years and applied a stochastic model. The results obtained show that uncertainty in the research sector has a negative influence on the EG in Finland. The results also indicate the fact that, as uncertainty in the research sector increases, the distribution or allocation of human capital will shift from the research sector to the final goods sector. Moreover, it was also found that uncertainty has a negative impact on welfare. This study has significant implications for the R&amp;D sector in Finland, in the sense that it has the potential to guide the research sector towards improvement through an increase in the number of patents and the establishment of research institutions that can reduce impact of uncertainty

Utilising Located Functions to Model and Optimise Distributed Computations

With developments in Grid computing and Web based data storage the task of orchestrating computations is becoming ever more difficult. Identifying which of the available computation resources and datasets to use is not trivial: it requires reasoning about the problem itself and the cost of moving data to complete the computation efficiently. This paper presents a conceptual notation and performance model that enables e-researchers to reason about their computations and make choices about the best use of resources