Modelling Tap Water Consumer Ratio

Meltem Ekiz and Osman Ufuk Ekiz
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Meltem Ekiz: Department of Statistics, Faculty of Science, University of Gazi, Ankara 06560, Turkey
Osman Ufuk Ekiz: Department of Statistics, Faculty of Science, University of Gazi, Ankara 06560, Turkey

Mathematics, 2020, vol. 8, issue 9, 1-8

Abstract: Increasing population and the rising air temperatures are known as factors that cause water depletion in the watersheds. Therefore, it is important to accurately predict the future ratios of tap water consumers using the same watershed to the population living in the specified area, to produce better water policies and to take the necessary measures. Predictions can be made by a growth curve model (GCM). Parameter estimations of the GCM are usually based on the ordinary least square ( OLS ) estimator. However, the outlier presence affects the estimations and the predictions, which are obtained by using the estimated model. The present article attempts to construct first- and third-order GCMs with robust least median square ( LMS ) and M estimators to make short-term predictions of ratios of tap water consumers. According to the findings, parameter estimations of the models, the outliers, and the predictions vary with respect to the estimators. The M estimator for short-term predictions is suggested for use, due to its robustness against outlier points.

Keywords: growth curve model; outliers; robust estimators; tap water consumer ratio; prediction (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2020
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