Some Small Sample Tests of Significance for a Poisson Distribution

Rao, C. Radhakrishna; Chakravarti, I. M.

doi:10.2307/3001466

Cited by 149 publications

(60 citation statements)

References 6 publications

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“…1 shows a schematic layout of the experiment. The spectral fluence distribution of the 0° beam exhibits a prominent high-energy peak resulting from the direct reaction 9 Be(p,n) 9 B and a continuum produced by breakup reactions. The high-energy peak is strongly suppressed in the spectral fluence of the 16° beam, while the phase space distribution of the breakup continuum is not very different from that at 0°.…”

Section: Characterisation Of the Neutron Beamsmentioning

confidence: 99%

Rbe of 200 Mev Neutron Radiation for the Induction of Chromosomal Abberation in Human Lymphocytes

Nolte¹,

Dangendorf²,

Buffler³

et al. 2007

Proceedings of International Workshop on Fast Neutron Detectors and Applications — PoS(FNDA2006)

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2 Induction of dicentric chromosomes by 192 MeV neutronsR. NolteThe production of dicentric chromosomes in human lymphocytes by high-energy neutron radiation was studied at the neutron beam facility of iThemba Laboratory using a quasimonoenergetic 192 MeV neutron beam. The linear yield coefficient of the linear dose-response relationship for dicentric chromosomes was measured to be (0.096 ± 0.020) Gy -1. This confirms our earlier observations that the yield of dicentric chromosomes decreases with increasing neutron energy above 400 keV and is almost constant above 20 MeV. Using the linear-quadratic dose-response relationship for dicentric chromosomes established in blood of the same donor for 60 Co γ-rays as reference radiation, an average maximum low-dose RBE (RBE M ) of 9 ± 3 for 192MeV quasi-monoenergetic neutrons, with a dose-weighted average energy of 162.1 MeV, was obtained. The yield of chromosome aberrations due to neutrons from the low-energy breakup continuum of the quasi-monoenergetic neutron spectrum was determined by an additional measurement at a neutron emission angle of 16° where the high-energy peak is strongly suppressed. Using this technique, a yield coefficient α = (0.121 ± 0.026) Gy -1 and an RBE M of 12 ± 4 for virtually monoenergtic 192 MeV neutrons was determined. The increased uncertainties result from the application of the (0°-16°) difference method.

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Section: Characterisation Of the Neutron Beamsmentioning

confidence: 99%

Rbe of 200 Mev Neutron Radiation for the Induction of Chromosomal Abberation in Human Lymphocytes

Nolte¹,

Dangendorf²,

Buffler³

et al. 2007

Proceedings of International Workshop on Fast Neutron Detectors and Applications — PoS(FNDA2006)

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“…Later (Rao and Chakravarti 1956) (Rao and Chakravarti 1956) it is stated that "is preferable to D for discriminating a compound Poisson distribution from a simple Poisson". The f 0 test has been recently studied in depth by (Fernández-Fontelo et al 2017).…”

Section: Exact Tests For Poisson Distributionmentioning

confidence: 99%

“…These tests are based on different properties of the Poisson model, as the equi-dispersion (the variance equals to the mean) and the frequency of zeros. The general asymptotic goodness-of-fit test (the classical χ 2 -test) for the Poisson distribution is not used here because it has been proved to be inaccurate for small samples, particularly for the case of chromosomal aberration counts (Rao and Chakravarti 1956;Savage 1970;Merkle 1981). The u-test is asymptotic, because it is not based on the exact distribution of a measure (for instance the dispersion index) and it is based on the normal approximation of an exact distribution.…”

Section: Introductionmentioning

confidence: 99%

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A note on Poisson goodness-of-fit tests for ionizing radiation induced chromosomal aberration samples

Higueras

González

Giorgio³

et al. 2018

International Journal of Radiation Biology

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Purpose: To present Poisson exact goodness-of-fit tests as alternatives and complements to the asymptotic u-test, which is the most widely used in cytogenetic biodosimetry, to decide whether a sample of chromosomal aberrations in blood cells comes from an homogeneous or inhomogeneous exposure. Results: It is observed how the u-test is not an appropriate approximation in small samples with small yield of chromosomal aberrations. Tools are provided to compute the three exact tests, which is not as trivial as the implementation of the u-test. Materials and Methods Conclusions:Poisson exact goodness-of-fit tests should be considered jointly to the u-test for detecting inhomogeneous exposures in the cytogenetic biodosimetry practice.

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“…Achromatic lesions (gaps) were not elevated as true chromosomal aberrations (Mace et al, 1978;Savage, 2004). Chromosomal aberration frequency differences between groups were analyzed using a small sample test of significance for a Poisson distribution (Rao and Chakravarti, 1956) and the Pearson coefficient of correlation to analyze the association between chromosomal aberration frequency and both exposure time and age.…”

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confidence: 99%

Chromosomal aberrations in peripheral lymphocytes from male native miners working in the Peruvian Andes

2007

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We analyzed the frequency of chromosomal aberrations in peripheral lymphocytes from underground miners from the Casapalca (n = 8, mean age = 45 y, range = 36 y to 55 y) and Bellavista (n = 8, mean age = 28 y, range 23 y to 34 y) high-altitude mining camps in the Peruvian Andes. This population was occupationally exposed to heavy metals such as lead and zinc as well as diesel emission particles, organic solvents and mine dust. The control groups consisted of individuals from a high altitude farming community in the Peruvian village of Tinco (n = 8, mean age = 37 y, range = 25 y to 52 y) and the sea level city of Lima (n = 14, mean age = 26 y, range = 20 y to 35 y). All individuals were male native Peruvians. A significantly higher incidence (1.88%, p < 0.05) of chromosomal aberrations (chromatid deletions and breaks, chromosome breaks and acentric fragments) were detected in lymphocytes from miners at the Casapalca camp as compared to miners from the Bellavista camp (0.5%, chromatid deletions and acentric fragments only) and the Lima sea level (0.07%, chromatid deletions only) and Tinco high altitude (no aberrations) controls. These results suggest that male native Peruvians occupationally exposed to underground mining activity have an increased frequency of chromosomal aberrations, which could be related to both age and exposure time. The increased chromosomal damage observed in the mining populations studied may be attributable to the complex mixture of genotoxic agents to which the miners may have been exposed. Chromosomal aberrations in human peripheral lymphocytes are well-established biomarkers of exposure to occupational or environmental genotoxic agents, cytogenetic analyses of lymphocytes from populations occupationally exposed to such agents having shown increased chromosomal aberration frequencies (Deknudt et al., 1973;Bauchinger et al., 1976;Lazutka et al., 1999;Topaktas et al., 2002). Underground miners are particularly exposed to complex mixtures of chemicals (e.g., heavy metals, diesel emission particles and dust), many of which are known mutagens (Johnson, 1998;Keshava and Ong, 1999;Rojas et al., 1999;Scheepers et al., 2002;Wolf et al., 2004;Donbak et al., 2005). Peruvian miners normally work at high altitude without any appropriate protective equipment, with chronic mountain sickness (excessive erythrocytosis caused by long term exposure to high altitude), silicosis and tuberculoses having frequently been reported in such workers (Paitán, 1965;León-Velarde and Arregui, 1992).Despite the fact that there are large numbers of underground miners in Peru there have been no published studies regarding the occupational exposure of these workers to genotoxic agents, one reason being the very difficult access to blood samples from these workers who are mainly native Andeans known for their aversion to blood extraction procedures.We report the results of the cytogenetic analysis of chromosomal aberrations in peripheral blood lymphocytes from a group of native Peruvian miners working at high altitud...

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Some Small Sample Tests of Significance for a Poisson Distribution

Cited by 149 publications

References 6 publications

Rbe of 200 Mev Neutron Radiation for the Induction of Chromosomal Abberation in Human Lymphocytes

Rbe of 200 Mev Neutron Radiation for the Induction of Chromosomal Abberation in Human Lymphocytes

A note on Poisson goodness-of-fit tests for ionizing radiation induced chromosomal aberration samples

Chromosomal aberrations in peripheral lymphocytes from male native miners working in the Peruvian Andes

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