A Statistical Test to Show Negligible Trend

Dixon, Philip M.; Pechmann, Joseph H. K.

doi:10.1890/04-1343

Cited by 83 publications

(91 citation statements)

References 21 publications

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“…Third, our definition of the noncritical effect is somewhat arbitrary and does not fully include information about data variations. The use of an equivalence test (e.g., Dixon and Pechmann 2005) would be valuable if the unacceptable effect size (critical effect size, see Munkittrick et al 2009) can be specified. However, it is difficult to specifically determine such effect sizes.…”

Section: Discussionmentioning

confidence: 99%

Responses of Riverine Macroinvertebrates to Zinc in Natural Streams: Implications for the Japanese Water Quality Standard

Iwasaki

Kagaya

Miyamoto

et al. 2011

Water Air Soil Pollut

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We conducted a field survey in Japanese streams and rivers to generate useful information about whether the Japanese water quality standard for zinc (Zn) in the freshwater environment (30 μg/L) is over-or underprotective of the populations and communities of lotic benthic macroinvertebrates. Many macroinvertebrate populations were reduced and community characteristics were altered at two polluted sites with Zn concentrations above 1,000 μg/L as compared with control sites with Zn concentrations below 30 μg/L. In contrast, at least one site among three polluted sites with Zn concentrations of 80-126 μg/L experienced noncritical effects (i.e., no significant difference was observed between the sample mean at a polluted site and that at the control sites, and the sample mean was within the minimum-maximum range of those at the control sites) for most of the ten community metrics for diversity and abundance. In addition, the abundances of 95% of the dominant taxa were not always significantly lower at more than one polluted site (Zn concentrations, ≥80 μg/L). Our results suggest that Zn concentrations below approximately 100 μg/L are likely to protect most aspects of richness and abundance of the riverine macroinvertebrate communities in the study areas. This study shows a case that the Japanese Zn standard is likely overprotective of the macroinvertebrate populations and communities.

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Section: Discussionmentioning

confidence: 99%

Responses of Riverine Macroinvertebrates to Zinc in Natural Streams: Implications for the Japanese Water Quality Standard

Iwasaki

Kagaya

Miyamoto

et al. 2011

Water Air Soil Pollut

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“…We used false discovery rate control (FDR; Benjamini andHochberg 1995, Garcia 2004) to correct for multiple statistical tests within each seasonal community. We also used equivalence tests to examine if macroecological patterns were significantly similar across treatments (Dixon and Pechmann 2005; see Appendix C for details). SAD, STR, and SAR are interrelated measures of community structure (Storch et al 2008).…”

Section: Statistical Approachmentioning

confidence: 99%

An experimental test of the response of macroecological patterns to altered species interactions

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Xiao

Ernest

et al. 2012

Ecology

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Abstract. Macroecological patterns such as the species-area relationship (SAR), the species-abundance distribution (SAD), and the species-time relationship (STR) exhibit regular behavior across ecosystems and taxa. However, determinants of these patterns remain poorly understood. Emerging theoretical frameworks for macroecology attempt to understand this regularity by ignoring detailed ecological interactions and focusing on the influence of a small number of community-level state variables, such as species richness and total abundance, on these patterns. We present results from a 15-year rodent removal experiment evaluating the response of three different macroecological patterns in two distinct annual plant communities (summer and winter) to two levels of manipulated seed predation. Seed predator manipulations significantly impacted species composition on all treatments in both communities, but did not significantly impact richness, community abundance, or macroecological patterns in most cases. However, winter community abundance and richness responded significantly to the removal of all rodents. Changes in richness and abundance were coupled with significant shifts in macroecological patterns (SADs, SARs, and STRs). Because altering species interactions only impacted macroecological patterns when the state variables of abundance and richness also changed, we suggest that, in this system, local-scale processes primarily act indirectly through these properties to determine macroecological patterns.

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“…Increasing α is wise if the population of interest is threatened by inaction (Gryska et al 1997;Daulwater et al 2009) because a greater α improves the survey's ability to detect population trends at the cost of increasing the probability of a false detection. Additionally, tests for negligible trend can be used as a complement to traditional hypothesis testing (Dixon and Pechmann 2005). With this method, the alternative hypothesis tests whether the 90% confidence interval falls within a specified (by the researcher) interval around zero.…”

Section: Discussionmentioning

confidence: 99%

“…With this method, the alternative hypothesis tests whether the 90% confidence interval falls within a specified (by the researcher) interval around zero. As such, it is possible for poorly estimated trends to be not significantly different from zero and not significantly negligible with the same level of confidence for both tests (Dixon and Pechmann 2005). The event variance component was estimated to be negative by the mixed model used to estimate variance components for the three levels of sampling in surveys for DHP larvae.…”

Section: Discussionmentioning

confidence: 99%

Using variance components to estimate power in a hierarchically nested sampling design

Dzul

Dixon

Quist

et al. 2012

Environ Monit Assess

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We used variance components to assess allocation of sampling effort in a hierarchically nested sampling design for ongoing monitoring of early life history stages of the federally endangered Devils Hole pupfish (DHP) (Cyprinodon diabolis). Sampling design for larval DHP included surveys (5 days each spring 2007-2009), events, and plots. Each survey was comprised of three counting events, where DHP larvae on nine plots were counted plot by plot. Statistical analysis of larval abundance included three components: (1) evaluation of power from various sample size combinations, (2) comparison of power in fixed and random plot designs, and (3) assessment of yearly differences in the power of the survey. Results indicated that increasing the sample size at the lowest level of sampling represented the most realistic option to increase the survey's power, fixed plot designs had greater power than random plot designs, and the power of the larval survey varied by year. This study provides an example of how monitoring efforts may benefit from coupling variance components estimation with power analysis to assess sampling design. Abstract We used variance components to assess allocation of sampling effort in a hierarchically nested sampling design for ongoing monitoring of early life history stages of the federally endangered Devils Hole pupfish (DHP) (Cyprinodon diabolis). Sampling design for larval DHP included surveys (5 days each spring 2007-2009), events, and plots. Each survey was comprised of three counting events, where DHP larvae on nine plots were counted plot by plot. Statistical analysis of larval abundance included three components:(1) evaluation of power from various sample size combinations, (2) comparison of power in fixed and random plot designs, and (3) assessment of yearly differences in the power of the survey. Results indicated that increasing the sample size at the lowest level of sampling represented the most realistic option to increase the survey's power, fixed plot designs had greater power than random plot designs, and the power of the larval survey varied by year. This study provides an example of how monitoring efforts may benefit from coupling variance components estimation with power analysis to assess sampling design.

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A Statistical Test to Show Negligible Trend

Cited by 83 publications

References 21 publications

Responses of Riverine Macroinvertebrates to Zinc in Natural Streams: Implications for the Japanese Water Quality Standard

Responses of Riverine Macroinvertebrates to Zinc in Natural Streams: Implications for the Japanese Water Quality Standard

An experimental test of the response of macroecological patterns to altered species interactions

Using variance components to estimate power in a hierarchically nested sampling design

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