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Meta-analysis as a statistical tool ...

Amenumey, Sheila Esi.

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Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management./
Author:	Amenumey, Sheila Esi.
Description:	184 p.
Notes:	Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: 5396.
Contained By:	Dissertation Abstracts International70-09B.
Subject:	Hydrology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3371823
ISBN:	9781109336085

Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management.
Amenumey, Sheila Esi.

Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management. - 184 p.

Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: 5396.

Thesis (Ph.D.)--University of Minnesota, 2009.

Agricultural drainage is the use of surface ditches, subsurface perforated pipes, or both, to remove standing or excess water from poorly drained lands. A meta-analysis was conducted with synthetic data simulated with DRAINMOD and with observed data gathered from literature to evaluate the effectiveness of drainage design and management. Previous work suggests meta-analysis can increase the statistical power for deducing treatment effects by reducing the population variance and corresponding confidence intervals, thus, increasing the precision of the effect size. With synthetic data, the usefulness of meta-analysis was assessed for drainage designs by comparing meta-analysis results to those obtained with a conventional analysis of variance approach. The results showed that given the same sample size, power to detect an effect using meta-analysis was 10% to 40% greater when compared to the results obtained by the analysis of variance. The results also showed that compared to the standardized mean difference, the log-response ratio effect size was a better index of effect size for drainage studies. A second meta-analysis was performed with observed data from fifty-three observations obtained from 20 studies published between 1979 and 2008. When viewed collectively, these 20 studies reported reductions in annual drainage volume from -8% to 95%. To investigate the potential factors on which effectiveness depends, a meta-analysis was performed to qualitatively and quantitatively aggregate the effect of controlled drainage using log-response effect size. A cumulative meta-analysis demonstrated that with fifty-three observations, the confidence interval values for the observed mean annual drainage volume reduction were reduced by 63% from the original study in 1979. The cumulative meta-analysis indicated that overall, controlled drainage is effective and its mean effect of 47% reduction in annual drainage volume could have been realized about eight years ago, but with less precision. The effect size was further evaluated on a categorical basis, using categories of soil type, location, and crop type. The mean effect of controlled drainage by location and soil factor were the most influential of all the factors considered. The categorical meta-analysis result of location suggested that local climatic variables such as precipitation, growing season, and humidity substantially influence the effectiveness of controlled drainage to reduce annual drainage volumes.

ISBN: 9781109336085Subjects--Topical Terms:

545716
Hydrology.

Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management.
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100 1 $a Amenumey, Sheila Esi. $3 1681277
245 1 0 $a Meta-analysis as a statistical tool for evaluating the hydrologic effects of subsurface drainage design and water table management.
300 $a 184 p.
500 $a Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: 5396.
500 $a Advisers: Gary R. Sands; Bruce N. Wilson.
502 $a Thesis (Ph.D.)--University of Minnesota, 2009.
520 $a Agricultural drainage is the use of surface ditches, subsurface perforated pipes, or both, to remove standing or excess water from poorly drained lands. A meta-analysis was conducted with synthetic data simulated with DRAINMOD and with observed data gathered from literature to evaluate the effectiveness of drainage design and management. Previous work suggests meta-analysis can increase the statistical power for deducing treatment effects by reducing the population variance and corresponding confidence intervals, thus, increasing the precision of the effect size. With synthetic data, the usefulness of meta-analysis was assessed for drainage designs by comparing meta-analysis results to those obtained with a conventional analysis of variance approach. The results showed that given the same sample size, power to detect an effect using meta-analysis was 10% to 40% greater when compared to the results obtained by the analysis of variance. The results also showed that compared to the standardized mean difference, the log-response ratio effect size was a better index of effect size for drainage studies. A second meta-analysis was performed with observed data from fifty-three observations obtained from 20 studies published between 1979 and 2008. When viewed collectively, these 20 studies reported reductions in annual drainage volume from -8% to 95%. To investigate the potential factors on which effectiveness depends, a meta-analysis was performed to qualitatively and quantitatively aggregate the effect of controlled drainage using log-response effect size. A cumulative meta-analysis demonstrated that with fifty-three observations, the confidence interval values for the observed mean annual drainage volume reduction were reduced by 63% from the original study in 1979. The cumulative meta-analysis indicated that overall, controlled drainage is effective and its mean effect of 47% reduction in annual drainage volume could have been realized about eight years ago, but with less precision. The effect size was further evaluated on a categorical basis, using categories of soil type, location, and crop type. The mean effect of controlled drainage by location and soil factor were the most influential of all the factors considered. The categorical meta-analysis result of location suggested that local climatic variables such as precipitation, growing season, and humidity substantially influence the effectiveness of controlled drainage to reduce annual drainage volumes.
590 $a School code: 0130.
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710 2 $a University of Minnesota. $b Water Resources Science. $3 1024533
773 0 $t Dissertation Abstracts International $g 70-09B.
790 1 0 $a Sands, Gary R., $e advisor
790 1 0 $a Wilson, Bruce N., $e advisor
790 1 0 $a Mulla, David J. $e committee member
790 1 0 $a Nieber, John L. $e committee member
790 1 0 $a Swenson, John B. $e committee member
790 $a 0130
791 $a Ph.D.
792 $a 2009
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