Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Statistical Analysis in Practice

As mentioned elsewhere, it is good scientific practice to pre-specify the main methods of statistical analysis in the protocol, but just because something is specified in the protocol it does not mean that it is correct. So again the answer is no. [Pg.126]

This chapter presents the fundamental principles of probabiUty theory and briefly examines the use of statistical analysis in the practice of system safety. The information discussed here should provide the reader with a very basic understanding of these concepts, which, by some accounts, is essential to the overall understanding of the system safety discipline. It should be noted that it is not within the scope of this Basic Guide to System Safety to provide aU there is to know regarding probability theory and statistical analysis. However, a certain level of understanding is essential and will therefore be discussed here. [Pg.56]

The test results we have obtained in the past are acceptable for specification purposes although considerable improvement is needed. We shall obtain data in the near future to see if a statistical analysis is practical. [Pg.44]

The data used to generate the maps is taken from a simple statistical analysis of the manufacturing process and is based on an assumption that the result will follow a Normal distribution. A number of component characteristics (for example, a length or diameter) are measured and the achievable tolerance at different conformance levels is calculated. This is repeated at different characteristic sizes to build up a relationship between the characteristic dimension and achievable tolerance for the manufacture process. Both the material and geometry of the component to be manufactured are considered to be ideal, that is, the material properties are in specification, and there are no geometric features that create excessive variability or which are on the limit of processing feasibility. Standard practices should be used when manufacturing the test components and it is recommended that a number of different operators contribute to the results. [Pg.54]

Practical considerations usually limit the number of replicate specimens of each kind that can be exposed for each period of test. At least two are recommended for obvious reasons, and if a larger number can be accommodated in the programme more valuable results can be secured—especially when it is desired to establish the reality of small differences in performance. For statistical analysis, five replicates are desirable. Accounts of statistical planning and analysis are given by F. H. Haynie in Reference 2 and in ASTM 016 1984. [Pg.981]

In practice, the number of soil samples that is actually analyzed is reduced by the preparation of composite samples. Here, multiple samples from a given replication and sampling period are blended together to yield one composite sample for analysis. Composite samples are statistically justifiable as they increase the precision with... [Pg.852]

Our finding that linewidth anisotropy in biomolecular EPR spectra can be described by a statistical theory in which the random variables that cause the broadening are fully correlated, does not only make analysis by simulation practical it also holds a message on the nature of the ultimate source of the broadening if the three principal elements of the p-tensor are fully correlated, then they should find their cause in a single, scalar quantity. [Pg.162]

Quantification of the limits of detection (LOD), or minimum detectable levels (MDL statistically defined in Section 13.4), is an important part of any analysis. They are used to describe the smallest concentration of each element which can be determined, and will vary from element to element, from matrix to matrix, and from day to day. Any element in a sample which has a value below, or similar to, the limits of detection should be excluded from subsequent interpretation. A generally accepted definition of detection limit is the concentration equal to a signal of twice (95% confidence level) or three times (99% confidence) the standard deviation of the signal produced by the background noise at the position of the peak. In practice, detection limits in ICP-MS are usually based on ten runs of a matrix matched blank and a standard. In this case ... [Pg.204]

In most natural situations, physical and chemical parameters are not defined by a unique deterministic value. Due to our limited comprehension of the natural processes and imperfect analytical procedures (notwithstanding the interaction of the measurement itself with the process investigated), measurements of concentrations, isotopic ratios and other geochemical parameters must be considered as samples taken from an infinite reservoir or population of attainable values. Defining random variables in a rigorous way would require a rather lengthy development of probability spaces and the measure theory which is beyond the scope of this book. For that purpose, the reader is referred to any of the many excellent standard textbooks on probability and statistics (e.g., Hamilton, 1964 Hoel et al., 1971 Lloyd, 1980 Papoulis, 1984 Dudewicz and Mishra, 1988). For most practical purposes, the statistical analysis of geochemical parameters will be restricted to the field of continuous random variables. [Pg.173]


See other pages where Statistical Analysis in Practice is mentioned: [Pg.30]    [Pg.30]    [Pg.39]    [Pg.30]    [Pg.30]    [Pg.39]    [Pg.128]    [Pg.691]    [Pg.47]    [Pg.773]    [Pg.124]    [Pg.706]    [Pg.523]    [Pg.524]    [Pg.524]    [Pg.504]    [Pg.36]    [Pg.365]    [Pg.314]    [Pg.130]    [Pg.182]    [Pg.14]    [Pg.104]    [Pg.263]    [Pg.84]    [Pg.35]    [Pg.37]    [Pg.13]    [Pg.253]    [Pg.23]    [Pg.53]    [Pg.60]    [Pg.86]    [Pg.200]    [Pg.308]    [Pg.365]    [Pg.188]    [Pg.873]    [Pg.889]    [Pg.148]    [Pg.232]   


SEARCH



Statistical analysis

© 2024 chempedia.info