Now showing items 1-20 of 29

    • Add or multiply? : A tutorial on ranking and choosing with multiple criteria 

      Tofallis, C. (University of Hertfordshire, 2014)
      Simple additive weighting is a well-known method for scoring and ranking alternative options based on multiple attributes. However the pitfalls associated with this approach are not widely appreciated. For example, the ...
    • Add or Multiply? : A Tutorial on Ranking and Choosing with Multiple Criteria 

      Tofallis, C. (2014-05-27)
      Simple additive weighting is a well-known method for scoring and ranking alternative options based on multiple attributes. However, the pitfalls associated with this approach are not widely appreciated. For example, the ...
    • Assessing charities using data envelopment analysis. 

      Tofallis, C.; Sargeant, A. (Cranfield, Centre for Business Performance, 2000)
      Data envelopment analysis (DEA) is a technique that takes account of multiple inputs and outputs to assess the relative efficiency of organisational units. Unlike regression its assessments are not based on any average but ...
    • An automatic-democratic approach to weight setting for the new human development index 

      Tofallis, C. (University of Hertfordshire, 2012)
      Perhaps the most difficult aspect of constructing a multi-dimensional index is that of choosing weights for the components. This problem is often bypassed by adopting the ‘agnostic’ option of equal weights, as in the Human ...
    • An automatic-democratic approach to weight setting for the new human development index. 

      Tofallis, C. (2013)
      Perhaps the most difficult aspect of constructing a multi-dimensional index is that of choosing weights for the components. This problem is often bypassed by adopting the ‘agnostic’ option of equal weights, as in the Human ...
    • A better measure of relative prediction accuracy for model selection and model estimation 

      Tofallis, C. (2015-08-01)
      Surveys show that the mean absolute percentage error (MAPE) is the most widely used measure of forecast accuracy in businesses and organizations. It is however, biased: When used to select among competing prediction methods ...
    • Chaotic behaviour in a bank account 

      Tofallis, C. (1995)
      This paper presents a very simple one variable model, apparently not previously studied, of a bank account with no random elements yet which displays chaos. Interest is periodically added to the account and when the balance ...
    • Combining two approaches to efficiency assessment 

      Tofallis, C. (2001)
      The advent of data envelopment analysis (DEA) enabled the measurement of efficiency to be extended to the case of multiple outputs. Prior to DEA we had the parametric approach based on multiple regression. We highlight ...
    • A different approach to university rankings 

      Tofallis, C. (2012-01)
      Educationalists are well able to find fault with rankings on numerous grounds and may reject them outright. However, given that they are here to stay, we could also try to improve them wherever possible. All currently ...
    • A different approach to university rankings (WP) 

      Tofallis, C. (University of Hertfordshire, 2011)
      Educationalists are well able to find fault with rankings on numerous grounds and may reject them outright. However, given that they are here to stay, we could also try to improve them wherever possible. All currently ...
    • Estimating Invariant Principal Components Using Diagonal Regression 

      Leznik, M.; Tofallis, C. (University of Hertfordshire, 2005)
      In this work we apply the method of diagonal regression to derive an alternative version of Principal Component Analysis (PCA). Diagonal regression was introduced by Ragnar Frisch (the first economics Nobel laureate) in ...
    • Fitting equations to data with the perfect correlation relationship 

      Tofallis, C. (University of Hertfordshire, 2015-12-23)
      We present a simple method for estimating a single relationship between multiple variables, which are all treated symmetrically i.e. there is no distinction between dependent and independent variables. This is of interest ...
    • Improving discernment in DEA using profiling 

      Tofallis, C. (1996)
      The failure of data envelopment analysis to provide adequate discrimination between a small number of alternatives is illustrated using a facility location problem. A straightforward modification which finds a desirability ...
    • Input efficiency profiling: an application to airlines 

      Tofallis, C. (1997)
      Data envelopment analysis (DEA) can produce results which lack discrimination, one consequence of this is that a large proportion of decision-making units (DMUs) appear to be efficient. In addition, because it is a radial ...
    • Investment Volatility : A Critique of Standard Beta Estimation and a Simple Way Forward 

      Tofallis, C. (University of Hertfordshire, 2004)
      Thanks are due to Markus Becker for useful comments on an earlier version of this essay. Beta is a widely used quantity in investment analysis. We review the common interpretations that are applied to beta in finance and ...
    • Investment Volatility : A critique of standard beta estimation and a simple way forward 

      Tofallis, C. (2008)
      Beta is a widely used quantity in investment analysis. We review the common interpretations that are applied to beta in finance and show that the standard method of estimation – least squares regression – is inconsistent ...
    • Least Squares Percentage Regression 

      Tofallis, C. (2008-11)
      In prediction, the percentage error is often felt to be more meaningful than the absolute error. We therefore extend the method of least squares to deal with percentage errors, for both simple and multiple regression. Exact ...
    • Least Squares Percentage Regression 

      Tofallis, C. (University of Hertfordshire, 2007)
      The percentage error, or error relative to the observed value is usually felt to be more meaningful than the absolute error - yet is rarely used in the fitting of least squares regression models. We therefore explore least ...
    • Model building with multiple dependent variables and constraints 

      Tofallis, C. (1999)
      The most widely used method for finding relationships between several quantities is multiple regression. This however is restricted to a single dependent variable. We present a more general method which allows models to ...
    • Model fitting for multiple variables by minimising the geometric mean deviation 

      Tofallis, C. (Springer Nature, 2002)
      We consider the problem of fitting a linear model for a number of variables but without treating any one of these variables as special, in contrast to regression where one variable is singled out as being a dependent ...