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Inter-rater and test,retest reliability of three contingent valuation question formats in south-east Nigeria

HEALTH ECONOMICS, Issue 5 2005
Obinna Onwujekwe
Abstract This paper examines the inter-rater and test,retest reliability of willingness to pay (WTP) for insecticide-treated mosquito nets and net re-treatment using the bidding game (BG), binary with follow-up (BWFU) and a novel structured haggling technique (SH). Inter-rater reliability was evaluated by having two sets of interviewers administer questionnaires to 109 (BG), 110 (BWFU) and 103 (SH) randomly selected household heads. Test,retest reliability was investigated by repeating interviews on 146 (BG), 161 (BWFU) and 139 (SH) household heads one month after an initial survey. Data analysis used testing of means, Spearman's correlation and Pearson's correlation coefficient for test of reliability, while non-parametric analysis was used to determine factors causing a variation in WTP. The study was conducted in Southeast Nigeria. Inter-rater reliability coefficients were estimated for the individual's WTP for own nets, WTP for others and WTP for re-treatment. Using WTP for own nets as the best reliability estimate, the coefficients were high at values of 0.77 (C.I. 0.72,0.86), 0.75 (C.I. 0.64,0.81) and 0.74 (C.I. 0.63,0.82) in the BG, BWFU and SH, respectively. In test,retest reliability coefficients, the coefficients for WTP for own nets were low-to-moderate at values of 0.51 (C.I. 0.40,0.62), 0.41 (C.I. 0.28,0.53) and 0.56 (C.I. 0.41,0.65) for the BG, BWFU and SH groups, respectively. Factors such as gender, change in income, unplanned expenditures, stated WTP in first survey, time-to-think, external information, and subjecting respondents to more than one interview explained the lower test,retest reliability coefficients. We conclude that the CVM was reliable in the study area and the question formats had similar levels of reliability. The lower coefficients in the test,retest reliability were due to the influence of factors affecting demand that had changed in the intervening period. Standard formats for determining reliability within CVM should be developed for easy comparison of results from different studies. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Flight characteristics of birds:

IBIS, Issue 2 2001
I. radar measurements of speeds
This is the first part of a study on flight characteristics of birds and presents an annotated list of flight speeds of 139 western Palearctic species. All measurements were taken with the same tracking radar and corrected for wind influence according to radar-tracked wind-measuring balloons. Graphical presentation of the birds' air speeds emphasizes the wide variation of speeds within species and allows easy comparison between taxonomic groups, species, and types of flight. Unlike theoretical predictions, speeds increase only slightly with size. The larger species seem to be increasingly limited to speeds close to their speed of minimum power consumption Vmp',. Released birds, apparently reluctant to depart with migratory speed, fly at considerably lower speeds than migrating conspecifics. While large birds seem to be limited to speeds around Vmp', smaller birds seem to be capable of selecting between various speeds, approaching predicted Vmp, when tending to remain airborne at low cost, but flying at much higher speeds when tending to make best progress at low cost (around predicted speed of maximum range Vmr,). Predictions of air speeds by aerodynamic models proved to be too low for small birds because the models do not account for the gain in speed attained by the reduction in profile drag during bounding flight of small passerines. The models predict excessive speeds for large birds because the power output available for flight seems to decline much more with size than previously assumed. [source]

Systematic interpretation of cyclic nucleotide binding studies using KinetXBase

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 6 2008
Sonja Schweinsberg
Abstract Functional proteomics aims to describe cellular protein networks in depth based on the quantification of molecular interactions. In order to study the interaction of adenosine-3,,5,-cyclic monophosphate (cAMP), a general second messenger involved in several intracellular signalling networks, with one of its respective target proteins, the regulatory (R) subunit of cAMP dependent protein kinase (PKA), a number of different methods was employed. These include fluorescence polarisation (FP), isothermal titration calorimetry (ITC), surface plasmon resonance (SPR), amplified luminescence proximity homogeneous assay (ALPHA-screen), radioligand binding or activity-based assays. Kinetic, thermodynamic and equilibrium binding data of a variety of cAMP derivatives to several cAMP binding domains were integrated in a single database system, we called KinetXBase, allowing for very distinct data formats. KinetXBase is a practical data handling system for molecular interaction data of any kind, providing a synopsis of data derived from different technologies. This supports ongoing efforts in the bioinformatics community to devise formal concepts for a unified representation of interaction data, in order to enable their exchange and easy comparison. KinetXBase was applied here to analyse complex cAMP binding data and highly site-specific cAMP analogues could be identified. The software package is free for download by academic users. [source]

How should we quantify the performance of KPro's?

ACTA OPHTHALMOLOGICA, Issue 2009

Purpose To report a method of standardized data collection and reporting and statistical assessment that can be used for all KPro´s available on the market. The database (will be presented) should be , Usable for different types of KPro´s , Easily adaptable to changes in technique , Allow for complete entry of relevant data Methods Visual Acuity data should be reported in different international surgical centres in a standardized manner: Best spectacle corrected VA, unless BCVA only possible with CL (> useful time of wear). A complete entry of all relevant data is possible in this database. The statistical analysis should be agreed upon by all centres. For Survival Time = Retention of KPro > the Kaplan-Meier method For Visual Acuity over the Course of Time > the Monte-Carlo method Results A database will be demonstrated that can be used free of charge by all KPro centres interested. The VISUAL ACUITY BY TIME- INDEX (VAT- Index) will also be presented, whose theoretical basis published in: Journal of Theoretical Medicine, 2002 / 4, 183-190, W. Hitzl and G. Grabner [bdquo]Application of the Monte Carlo Method for the Assessment of Long-term Success in Keratoprosthesis Surgery". Example of its use will be give, based in data, courtesy Barraquer Eye Clinic, Barcelona. Conclusion With the Kaplan-Meier method: + analysis is done quickly, uses all data available, hypotheses tests are available for comparisons and mean and median survival time can be computed - no information about relation between time and best corrected visual acuity and the definition of terminal event is arbitrary to a certain extent. Monte-Carlo method (VAT-index): + Method is based on a so-called non-parametric longitudinal model + Reliabel estimation of relation between time and best corrected visual acuity at any given time point (patient as well as surgeon is basically interested in this relation). + statistically valid analysis and better comparison of different KPro techniques + easy comparison of defined postoperative periods + comparison of different initial clinical findings and diseases possible + long-time follow-up of BCVA - shorter follow-up time as compared with Kaplan-Meier method (e.g. with strict [bdquo]80%data complete" criteria) [source]