Assessment of Significance

This section provides an introduction to a variety of approaches for assessing significance. For historical reasons, some methods such as cross-validation and independent testing of models are best described in the chapters on multivariate methods (see Chapters 4 and 5), although the chemometrician should have a broad appreciation of all such approaches and not be restricted to any one set of methods. 

The design matrix simplifies considerably, and together with the corresponding regression coefficients is presented in Table 2.10. Now the coefficients are approximately on the same scale, and it appears that there are radical differences between these new numbers and the coefficients in Table 2.8. Some of the differences and their interpretation are listed below. 

Graph of estimated response versus pH at the central temperature of the design in Table 2.6 

Therefore, without taking great care, misleading conclusions can be obtained about file significance and influence of the different factors. It is essential that the user of simple chemometric software is fully aware of this, and always interprets numbers in terms of physical meaning. 

consider the 10 experiments at which bt is at a coded level of either +1 or — 1, namely the first 10 experiments  

---

Conducting global public health surveillance and assessment of significant public health events, and disseminating public health information to states, as appropriate... 

What constitutes a significant difference between two spectra When the differences are small, the answer depends on sample preparation and sample stability as well as accuracy of concentration determination, identification of and compensation for drift in the spectrometer, correct baseline correction, absence of bubbles in the sample, reproducible cleanliness of the cuvette, and the level of general handling procedures. Ultimately, an assessment of significance depends on the experience, competence, and confidence of the operator. 

Forensic chemistry applies new and sensitive analytical methods in identification of traces and collects technological information about various materials to create a database. For the evaluation of results obtained, statistical methods enable assessment of significance of differences observed between the examined samples, as well as the statistical error. 

The evaluation and assessment of significance evaluates the relative importance of the predicted impacts to allow a focus on the main adverse impacts. 

A further consideration arose in 2008 with the promulgation of guidance requiring safety assessment of significant human metabolites including their safety pharmacology aspects [4]. 

Kjelldn, U. The deviation concept in occupational accident control. Part I Definition and classification and part II Data collection and assessment of significance. Accident Analysis Prevention 16 289-323, 1984. 

Because of the inherent variability in the length and branching neurites of control as well as experimental neurons, we use one-way analysis of variance (ANOVA) for statistical analysis of the data. Analysis of variance allows comparison of variability within as well as between samples, resulting in a more complete assessment of significant changes. 

Non-destructive testing assessment of significance of defects found. 

Kjellen, U. 1984. The Deviation Concept in Occupational Accident Control, Part I Definition and Classifieation and Part II Data CoUeetion and Assessment of Significance, Accident Anal Prev 16 289—323. 

The National system of accreditation gives much attention to the training and qualification of NDT personnel. Significant subjective component, such as training and qualification of personnel, is present in NDT implementation and assessment of its results, thus all specialists carrying out NDT must be certified in compliance with CTBEH 473. 

Excluding the phenomenon of hyperconjugation, the only other means by which electronic effects can be transmitted within saturated molecules, or exerted by inductive substituents in aromatic molecules, is by direct electrostatic interaction, the direct field effect. In early discussions of substitution this was usually neglected for qualitative purposes since it would operate in the same direction (though it would be expected to diminish in the order ortho > meta > para) as the cr-inductive effect and assessment of the relative importance of each is difficult however, the field effect was recognised as having quantitative significance. ... 

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Subchronic Studies. Although short-term repeated exposure studies provide valuable information about toxicity over this time span, they may not be relevant for assessment of ha2ard over a longer time period. For example, the minimum and no-effects levels determined by short-term exposure may be significantly lower if exposure to the test material is extended over several months. Also, certain toxic effects may have a latency which does not allow their expression or detection over a short-term repeated-exposure period for example, kidney dysfunction or disturbances of the blood-forming tissues may not become apparent until subchronic exposure studies are undertaken. 

Human Health Effects. Any assessment of adverse human health effects from PCBs should consider the route(s) of and duration of exposure the composition of the commercial PCB products, ie, degree of chlorination and the levels of potentially toxic PCDF contaminants. As a result of these variables, it would not be surprising to observe significant differences in the effects of PCBs on different groups of occupationally-exposed workers. 

Process Hazard Analysis (PHA) An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate rec-... 

Problems associated with interpretation of the results and assessing their significance are common... 

Stationary monitoring networks are also operated to determine the impact of new sources of emissions. As part of the environmental impact statement and Prevention of Significant Deterioration processes, the projected impact of a new source on existing air quality must be assessed. Air quality monitoring is one means of making this type of assessment. A monitoring network... 

If areas identified as likely to receive significant atmospheric contaminant concentrations include areas supporting edible biota, the biouptake of contaminants must be considered as a possible environmental fate pathway. Direct biouptake from the atmosphere is a potential fate mechanism for lipophilic contaminants. Biouptake from soil or water following transfer of contaminants to these media must also be considered as part of the screening assessments of these media. 

Condition and life assessment is significant for all types of plants, and especially Combined Cycle Power Plants. The most important aspect of a plant is high availability, and reliability, in some cases even more significant than higher efficiency. 

The new standard amended 29 Code of Eederal Regulations (CER) to include general requirements (29 CER 1910.132), eye and face protection (29 CER 1910.133), head protection (29 CER 1910.135), and foot protection (29 CER 1910.136). A new regulation (29 CER 1910.138) applied to hand protection. These changes are significant because they mandated employers to conduct a hazard assessment of the workplace to decide if hazards in the operation required the use of PPE. 

---