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Sample Size Requirements for Assessing Statistical Moments of Simulated Crop Yield Distributions
Institute for Environmental Decisions, Agrifood & Agri-environmental Economics Group, ETH Zurich, Sonneggstrasse 33/SOL C7, Zurich CH-8092, Switzerland
Agricultural Economics and Rural Policy Group, Wageningen University, Hollandseweg 1, Room 2114, NL-6706 KN Wageningen, The Netherlands
Air Pollution/Climate Group, Agroscope Research Station ART, Reckenholzstrasse 191, Zurich CH-8046, Switzerland
* Author to whom correspondence should be addressed.
Received: 27 November 2012; in revised form: 4 February 2013 / Accepted: 18 March 2013 / Published: 2 April 2013
Abstract: Mechanistic crop growth models are becoming increasingly important in agricultural research and are extensively used in climate change impact assessments. In such studies, statistics of crop yields are usually evaluated without the explicit consideration of sample size requirements. The purpose of this paper was to identify minimum sample sizes for the estimation of average, standard deviation and skewness of maize and winterwheat yields based on simulations carried out under a range of climate and soil conditions. Our results indicate that 15 years of simulated crop yields are sufficient to estimate average crop yields with a relative error of less than 10% at 95% confidence. Regarding standard deviation and skewness, sample size requirements depend on the degree of symmetry of the underlying population’s distribution. For symmetric distributions, samples of 200 and 1500 yield observations are needed to estimate the crop yields’ standard deviation and skewness coefficient, respectively. Higher degrees of asymmetry increase the sample size requirements relative to the estimation of the standard deviation, while at the same time the sample size requirements relative to the skewness coefficient are decreased.
Keywords: crop yield distributions; statistical moments; sample sizes requirements; crop models; stochastic weather generator; climate change
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Lehmann, N.; Finger, R.; Klein, T.; Calanca, P. Sample Size Requirements for Assessing Statistical Moments of Simulated Crop Yield Distributions. Agriculture 2013, 3, 210-220.
Lehmann N, Finger R, Klein T, Calanca P. Sample Size Requirements for Assessing Statistical Moments of Simulated Crop Yield Distributions. Agriculture. 2013; 3(2):210-220.
Lehmann, Niklaus; Finger, Robert; Klein, Tommy; Calanca, Pierluigi. 2013. "Sample Size Requirements for Assessing Statistical Moments of Simulated Crop Yield Distributions." Agriculture 3, no. 2: 210-220.