Statistical power calculation and sample size determination for environmental studies with data below detection limits

Shao, Quanxi & Wang, You-Gan (2009) Statistical power calculation and sample size determination for environmental studies with data below detection limits. Water Resources Research, 45(9), W09410-(1-8).

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Power calculation and sample size determination are critical in designing environmental monitoring programs. The traditional approach based on comparing the mean values may become statistically inappropriate and even invalid when substantial proportions of the response values are below the detection limits or censored because strong distributional assumptions have to be made on the censored observations when implementing the traditional procedures. In this paper, we propose a quantile methodology that is robust to outliers and can also handle data with a substantial proportion of below-detection-limit observations without the need of imputing the censored values. As a demonstration, we applied the methods to a nutrient monitoring project, which is a part of the Perth Long-Term Ocean Outlet Monitoring Program. In this example, the sample size required by our quantile methodology is, in fact, smaller than that by the traditional t-test, illustrating the merit of our method.

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1 citations in Scopus
1 citations in Web of Science®
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ID Code: 90453
Item Type: Journal Article
Refereed: Yes
Keywords: water-quality data, quantiles, regression
DOI: 10.1029/2008wr007563
ISSN: 0043-1397
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Deposited On: 17 Nov 2015 02:41
Last Modified: 17 Nov 2015 02:41

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