## Abstract

Since the prediction of environmental changes depends heavily on mathematical models, environmental planners have a definite need for a general test that can be easily applied to determine the reliability of a model or to choose between available models. In this paper a 'reliability index' for a model is defined. This index is a number k ≥ 1 which is determined from a set x_{1},x_{2},...,x_{n} of model predictions and a corresponding set y_{1},y_{2},...,y_{n} of observations. One interpretation of the index k is that the model predictions agree with observations, in some sense, within a factor of k. The index k is defined using an intuitive, geometric approach and is justified through agreement with another index developed using statistical techniques. Examples are given for a model which predicts the atmospheric movement of radon-222 originating from a concentrated source of radium-226, such as a uranium tailings pile.

Original language | English |
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Pages (from-to) | 303-312 |

Number of pages | 10 |

Journal | Ecological Modelling |

Volume | 13 |

Issue number | 4 |

DOIs | |

State | Published - Sep 1981 |

Externally published | Yes |

### Funding

We consider the problem of estimating the reliability of a model, given a set x~,x 2 .... ,x n of model predictions and a corresponding set Y~,Y2,... ,Yn of observations. Consider, as an example, the data given in Table I (Goldsmith and Clements, 1979). In this example a comparison is made between measured annual average radon-222 concentrations in Grand Junction, Colorado (where there is a uranium tailings pile), and concentrations predic- * Operated by Union Carbide Corporation under contract W-7405-eng-26 with the U.S. Department of Energy. ** Research partially supported by a summer faculty fellowship from Indiana University at South Bend.