China
Africa
Explore chapters and articles related to this topic
Air Quality Monitoring
Published in Béla G. Lipták, Analytical Instrumentation, 2018
R. A. Herrick, R. G. Smith, B. G. Lipták
The concentration of many air pollutants has been found to follow a log normal rather than a normal distribution. In a log normal distribution, a plot of the logarithm of the measured value more closely approximates the bell-shaped Gaussian distribution curve than does a plot of the numerical data. Suspended particulate concentrations are a prime example of this type of distribution. When this is the case, the geometric mean is the statistical parameter which best describes the population of data. The arithmetic mean is of limited value because it is dominated by a few occurrences of high values. The geometric mean, in combination with the geometric standard deviation, is a complete description of a frequency distribution for a log normally distributed pollutant.
Chapter 13 Mathematical and statistical techniques
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
The arithmetic mean uses all the data and is the ‘average’ value. Geometric mean is the ‘average’ value of transformed variables, usually a logarithmic transformation that is used for asymmetrical distributions. The median is a single data point, the ‘middle’ piece of data after it has been ranked in ascending order. The mode is the mid-point of the interval in which the highest frequency occurs. Strictly speaking, not all of the data are used to determine the median and mode.
Microbiological drinking water parameters
Published in Frank R. Spellman, The Drinking Water Handbook, 2017
Many National Pollutant Discharge Elimination System (NPDES) discharge permits require fecal coliform testing. Results for fecal coliform testing must be reported as a geometric mean (average) of all the test results obtained during a reporting period. A geometric mean, unlike an arithmetic mean or average, dampens the effect of very high or low values that otherwise might cause a non-representative result.
Design Factors of Guiding Aircraft Through Continuous Descent Operations: Pilot and Controller Perspectives
Published in The International Journal of Aerospace Psychology, 2019
Pilots control the movements of the maneuvering aircraft, whereas controllers must monitor aircraft dynamics within their station. The difference of opinions between pilots and controllers is a gap that the designers of the ATC procedure expect to shorten. The purpose of using FMCDM was to synthesize the final selection of preferred alternatives for all respondents. The fuzzy numbers for criteria cannot be compared because they are, in theory, not precise values; otherwise we would need to defuzzy all fuzzy numbers. This study additionally used geometric means of different groups to compare evaluated gaps between pilots and controllers for all criteria. In the sampling processes, the sampled numbers for different groups might not be the same. A benefit of using geometric mean over using arithmetic mean is that the geometric mean can avoid the influence of outliers in the samples.
Development, evaluation, and implementation of building downwash and plume rise enhancements in AERMOD
Published in Journal of the Air & Waste Management Association, 2022
Ron L. Petersen, James O. Paumier, Sergio A. Guerra
Table 4 shows the geometric mean of RHC ratios for both receptors. A geometric mean is used because extreme values do not affect the mean as much. Note: the geometric mean is calculated by multiplying the numbers altogether and then taking the nth root of the multiplied numbers, where n is the total number of data values. Hereafter, the “geometric mean or the RCH values” will be referred as the “average ratio.” Cleary for this database, PRIME2+ Ent performs best with an average ratio of 1.03. PRIME2 has the second-best overall agreement with an average ratio of 1.27. AERMOD and AERMOD+Ent on the other hand tend to under predict with average ratios of 0.77 and 0.66.
The geometric mean is a superior frequency response averaging method for human body vibration
Published in Ergonomics, 2021
Mohammad Fard, Jianchun Yao, Kazuhito Kato, John L. Davy
The geometric mean is the nth root of the product of the n measured values. By using the geometric mean method, the magnitude of the averaged transmissibility is defined in Equation (12) while the phase of the averaged transmissibility is given in Equation (13). Note that when averaging in the phase domain with any method, the phase needs to be unwrapped before averaging.