Sensitivity analysis for unmeasured confounders using an electronic spreadsheet

In studies assessing the effects of a given exposure variable and a specific outcome of interest, confusion may arise from the mistaken impression that the exposure variable is producing the outcome of interest, when in fact the observed effect is due to an existing confounder. However, quantitative techniques are rarely used to determine the potential influence of unmeasured confounders. Sensitivity analysis is a statistical technique that allows to quantitatively measuring the impact of an unmeasured confounding variable on the association of interest that is being assessed. The purpose of this study was to make it feasible to apply two sensitivity analysis methods available in the literature, developed by Rosenbaum and Greenland, using an electronic spreadsheet. Thus, it can be easier for researchers to include this quantitative tool in the set of procedures that have been commonly used in the stage of result validation.

WPMU to Wp3.1.3 Plugin compatibility spreadsheet

Assessment of Plugin compatibility through migration from WPMU 2.7.1 to WP3.1.3

Sheffield Rail Spreadsheet

This data contains the results of application of a feasibility study on rail demand. The case study of Sheffield and 100 large urban areas in the UK.

A note on the use of spreadsheet optimisers in real estate analysis

Modern Portfolio Theory (MPT) has been advocated as a more rational approach to the construction of real estate portfolios. The application of MPT can now be achieved with relative ease using the powerful facilities of modern spreadsheet, and does not necessarily need specialist software. This capability is to be found in the use of an add-in Tool now found in several spreadsheets, called an Optimiser or Solver. The value in using this kind of more sophisticated analysis feature of spreadsheets is increasingly difficult to ignore. This paper examines the use of the spreadsheet Optimiser in handling asset allocation problems. Using the Markowitz Mean-Variance approach, the paper introduces the necessary calculations, and shows, by means of an elementary example implemented in Microsoft's Excel, how the Optimiser may be used. Emphasis is placed on understanding the inputs and outputs from the portfolio optimisation process, and the danger of treating the Optimiser as a Black Box is discussed.

Computing Markowitz efficient frontiers using a spreadsheet optimiser

Markowitz showed that assets can be combined to produce an 'Efficient' portfolio that will give the highest level of portfolio return for any level of portfolio risk, as measured by the variance or standard deviation. These portfolios can then be connected to generate what is termed an 'Efficient Frontier' (EF). In this paper we discuss the calculation of the Efficient Frontier for combinations of assets, again using the spreadsheet Optimiser. To illustrate the derivation of the Efficient Frontier, we use the data from the Investment Property Databank Long Term Index of Investment Returns for the period 1971 to 1993. Many investors might require a certain specific level of holding or a restriction on holdings in at least some of the assets. Such additional constraints may be readily incorporated into the model to generate a constrained EF with upper and/or lower bounds. This can then be compared with the unconstrained EF to see whether the reduction in return is acceptable. To see the effect that these additional constraints may have, we adopt a fairly typical pension fund profile, with no more than 20% of the total held in Property. The paper shows that it is now relatively easy to use the Optimiser available in at least one spreadsheet (EXCEL) to calculate efficient portfolios for various levels of risk and return, both constrained and unconstrained, so as to be able to generate any number of Efficient Frontiers.

Biofuels impact on crop and food prices : using an interactive spreadsheet /

Mode of access: Internet.

Experiences in using a contingency factor-based validation methodology for spreadsheet DSS

The use of spreadsheets has become routine in all aspects of business with usage growing across a range of functional areas and a continuing trend towards end user spreadsheet development. However, several studies have raised concerns about the accuracy of spreadsheet models in general, and of end user developed applications in particular, raising the risk element for users. High error rates have been discovered, even though the users/developers were confident that their spreadsheets were correct. The lack of an easy to use, context-sensitive validation methodology has been highlighted as a significant contributor to the problems of accuracy. This paper describes experiences in using a practical, contingency factor-based methodology for validation of spreadsheet-based DSS. Because the end user is often both the system developer and a stakeholder, the contingency factor-based validation methodology may need to be used in more than one way. The methodology can also be extended to encompass other DSS.

A methodology for spreadsheet development based on data structure

Abstract not available

Teste de banco com carga continua para analise do volume de oxigenio (VO2) predito e analisado por tempo de esforço em pessoas treinadas (TRD), ativas (ATV) e destreinadas (DTR) a partir dos 13 anos : proposta de validação

Universidade Estadual de Campinas . Faculdade de Educação Física

Determinação de ácido acéttico em amostra de vinagre adulterada com ácido clorídrico - um experimento integrado de titulação potenciométrica e condutométrica

The determination of acetic acid in vinegar adulterated sample using simultaneous potentiometric and condutometric titrations was used as an example of integrated experiment in instrumental analysis. An Excel® spreadsheet, which allows the entry of simultaneous data and the construction of the superimposed experimental curves (condutometric, potentiometric, first and second derivative potentiometric curve and, distribution diagrama of the acetic species as function of pH), was used as powerful tool to discuss the fundamental concepts involved in each technique and choose the best of them to quantify, without mutual interference, H3CCOOH and HCl in vinegar adulterated sample.

Motivação de gestantes para o aleitamento materno

OBJETIVO: Conhecer os motivos de gestantes para o aleitamento materno. MÉTODOS: É um estudo qualitativo realizado com 164 gestantes assistidas no pré-natal em dois Centros de Saúde na região central da cidade de São Paulo. Os dados foram coletados por meio de entrevistas semi-estruturadas sobre motivação para amamentar. As narrativas foram organizadas em planilha eletrônica em busca de categorias. RESULTADOS: As principais categorias identificadas estavam relacionadas à saúde da criança, da mulher e aos benefícios da prática de amamentar e do leite materno. A maioria das mulheres (98,8%) foi favorável à amamentação. Benefícios à saúde da criança foi o motivo mais freqüente (73,8%). CONCLUSÃO: A motivação ao aleitamento materno foi centrada nos benefícios à saúde da criança. A amamentação é valorizada independentemente da vontade materna.