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  • 1
    Language: English
    In: Environmental Science and Pollution Research, 2013, Vol.20(10), pp.7341-7347
    Description: Although generally misunderstood, the p value is the probability of the test results or more extreme results given H 0 is true: it is not the probability of H 0 being true given the results. To obtain directly useful insight about H 0 , the positive predictive value (PPV) and the negative predictive value (NPV) may be useful extensions of null hypothesis significance testing (NHST). They provide information about the probability of statistically significant and non-significant test outcomes being true based on an a priori defined biologically meaningful effect size. The present study explores the utility of PPV and NPV in an ecotoxicological context by using the frequently applied Daphnia magna reproduction test (OECD guideline 211) and the chemical stressor lindane as a model system. The results indicate that especially the NPV deviates meaningfully between a test design strictly following the guideline and an experimental procedure controlling for α and β at the level of 0.05. Consequently, PPV and NPV may be useful supplements to NHST that inform the researcher about the level of confidence warranted by both statistically significant and non-significant test results. This approach also reinforces the value of considering α , β , and a biologically meaningful effect size a priori.
    Keywords: Sample size ; Bayesian ; Power analysis ; Effect size ; Type I error rate ; Type II error rate
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 2
    Language: English
    In: Environmental Science and Pollution Research, 2015, Vol.22(5), pp.3955-3957
    Description: We argued recently that the positive predictive value (PPV) and the negative predictive value (NPV) are valuable metrics to include during null hypothesis significance testing: They inform the researcher about the probability of statistically significant and non-significant test outcomes actually being true. Although commonly misunderstood, a reported p value estimates only the probability of obtaining the results or more extreme results if the null hypothesis of no effect was true. Calculations of the more informative PPV and NPV require a priori estimate of the probability ( R ). The present document discusses challenges of estimating R .
    Keywords: Sample size ; Bayesian ; Power analysis ; Effect size ; Type I error rate ; Type II error rate
    ISSN: 0944-1344
    E-ISSN: 1614-7499
    Library Location Call Number Volume/Issue/Year Availability
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  • 3
    Language: English
    In: Environmental Science and Pollution Research, 2018, Vol.25(21), pp.20911-20919
    Description: The impact of titanium dioxide nanoparticles (nano-TiO 2 ) on the bioavailability of metals in aquatic filter-feeding organisms has rarely been investigated, especially in the presence of algae as a food source. In this study, we quantified the accumulation and subcellular distribution of arsenate ( As V ) in Daphnia magna in the presence of nano-TiO 2 and a green alga ( Scenedesmus obliquus ) food source. Results showed that S. obliquus significantly increased the accumulation of total arsenic ( As ) and titanium ( Ti ) in D. magna . The presence of this food source increased As in metal-sensitive fractions (MSF) and as biologically detoxified metals (BDM), while it decreased Ti levels in MSF but increased levels as BDM. The difference in the subcellular distribution of As and Ti demonstrates the dissociation of As from nano-TiO 2 during digestion at subcellular partitioning irrespective of food availability. In turn, the presence of algae was shown to increase metal-based toxicity in D. magna due to the transfer of As from BMD to MSF. Furthermore, S. obliquus significantly increased the concentration of As and Ti in soluble fractions, indicating that As and nano-TiO 2 ingested by D. magna could be transferred more readily to their predators in the presence of S. obliquus . Our study shows the potential of algae to increase the toxicity and biomagnification of As V . Furthermore, it highlights food as an important factor in the toxicity assessment of nanomaterials and co-existing pollutants.
    Keywords: Nanoparticles ; Arsenic ; Bioavailability ; Subcellular distribution ; Algae
    ISSN: 0944-1344
    E-ISSN: 1614-7499
    Library Location Call Number Volume/Issue/Year Availability
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