Using percentile analysis for determination of alarm values

2002 ◽  
Vol 2 (2) ◽  
pp. 145-150
Author(s):  
R.C. Lake ◽  
P.A. Agutter ◽  
T. Burke
Keyword(s):  
Water Supply ◽  
Normal Operation ◽  
Distributed Data ◽  
Expert Group ◽  
Particle Counting ◽  
Counting Data ◽  
The Mean ◽  
Standard Deviations ◽  
Normally Distributed

The use of statistically derived alarm values for the minimisation of the risk of Cryptosporidium entering the water supply has been recommended in the report of the Bouchier expert group. Values derived using the mean plus standard deviations can be skewed by spikes, including those caused by filter washes. Indeed, theoretically, the use of standard deviations should only be used with normally distributed data. It is shown in this paper that turbidity and particle counting data is not normally distributed and that values derived by means of percentile analysis are more sensitive than using the mean plus standard deviations. Percentile analysis is able to produce alarms for data that is clearly different from normal operation, enabling smaller deviations from the usual to be identified. The values derived from one set of data are also shown to be appropriate for periods of around three months.

Gas Chromatographic/Nitrogen-Phosphorus Detection Method for Determination of Ethylene Thiourea in Finished Drinking Waters: Collaborative Study

1993 ◽  
Vol 76 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
James E Longbottom ◽  
Kenneth W Edgell ◽  
Elizabeth J Erb ◽  
Viorica Lopez-Avila ◽  
◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Drinking Water ◽  
Drinking Waters ◽  
Relative Standard ◽  
The Mean ◽  
Ethylene Thiourea ◽  
Standard Deviations ◽  
Nitrogen Phosphorus Detector ◽  
Nitrogen Phosphorus

Abstract A joint U.S. Environmental Protection Agency (USEPA)-AOAC interlaboratory method validation study was conducted on USEPA National Pesticide Survey (NPS) Method 6, "Determination of Ethylene Thiourea (ETU) in Finished Drinking Water by Gas Chromatography with a Nitrogen-Phosphorus Detector." The purpose of the study was to determine and compare the mean recoveries and precision for determination of ETU in reagent water and finished drinking waters. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with ETU at 6 concentrations levels, prepared as 3 Youden pairs. In the method, the test water is extracted by passing the sample through an absorbent matrix type tube. ETU is recovered from the tube with methylene chloride, the extract is solvent-exchanged to ethyl acetate, and an aliquot of each extract is analyzed by gas chromatography using a nitrogen-phosphorus detector. Twelve laboratories participated in the study. Data were analyzed using a USEPA computer program, which measured recovery and precision for ETU and compared the performance of the method between the 2 water types. Over the concentration range tested, the mean percent recoveries of ETU were 82-92% in reagent water and 85-98% in finished drinking water. The range of the betweenlaboratory relative standard deviations (RSDR) for the 6 concentrations was 5-24% in reagent water, but was only 4-9% in finished drinking water. The range of the within-laboratory relative standard deviations (RSDr) was 6-14% for reagent water and 6- 10% for finished drinking water. Results for the 2 water matrixes showed no statistically significant differences. The method has been adopted first action by AOAC International for determination of ETU in finished drinking waters.

Determination of Hydraulic and Hydrological Parameters of Available Streams in Okada Town and its Environs for Viable Source of Water Supply

2013 ◽  
Vol 824 ◽  
pp. 597-604
Author(s):  
Avemaria Matthew Eze ◽  
Maryann Ogoamaka Ezugwu ◽  
Tonye G. Okorie
Keyword(s):  
Water Supply ◽  
Hydraulic Parameters ◽  
Community Based ◽  
Hydrological Parameters ◽  
Commercial Area ◽  
Sustainable Water Supply ◽  
Edo State ◽  
The Mean ◽  
Discharge Method

The study area comprises Okada Town and its environs located in the South Western part of Edo State in Nigeria. The study area is primarily, an agricultural and commercial area with prospects of becoming a big town with attendant water supply problems. The study identified viable sources for sustainable community based water supply with the objectives to determine hydraulic parameters of the existing streams. The method used to measure the stream hydraulic parameters was Current Meter Discharge Method. The mean dry weather widths are: Okada Stream (3.6m and 10.2m at narrow and upstream sections); Iguedo and Okhai Streams (10.6m and 2.8m at typical upstream sections respectively). The corresponding stream stages and discharges are: Okada (0.57m; 100,656m3/day); Iguedo (1.23m; 117,590m3/day) and Okhai (0.21m; 8,294m3/day). From the obtained, and plotted data, the derived stream stage-discharge equations of the form Q = CHn are: Q = 1.543H0.5 for Okada Stream; Q = 1.062H1.2 for Iguedo Stream; and Q = 0.1334H0.21 for Okhai Stream. This study established only 1-year hydrological frequency. A 5-year or 10-year return period is needed for greater risks from probable worst condition scenarios. The recorded maximum combined discharge was 552,441m3/day in September 2011 and minimum flow was 226,540m3/day in January 2012. The reliable yield is estimated at 103,886m3/day and maximum allowable abstraction is 81,455m3/day. The results show that the three source streams will be adequate for sustainable water supply for the study area.

Some Aspects of Estimators for Variance of Normally Distributed Data

2015 ◽  
pp. 355-379
Author(s):  
N. Hemachandra ◽  
Puja Sahu
Keyword(s):  
Pareto Frontier ◽  
Distributed Data ◽  
Mean Square ◽  
Accuracy And Precision ◽  
Class Of Estimators ◽  
The Mean ◽  
Sample Variances ◽  
The One ◽  
Bias Versus ◽  
Normally Distributed

Normally distributed data arises in various contexts and often one is interested in estimating its variance. The authors limit themselves in this chapter to the class of estimators that are (positive) multiples of sample variances. Two important qualities of estimators are bias and variance, which respectively capture the estimator's accuracy and precision. Apart from the two classical estimators for variance, they also consider the one that minimizes the Mean Square Error (MSE) and another that minimizes the maximum of the square of the bias and variance, the minmax estimator. This minmax estimator can be identified as a fixed point of a suitable function. For moderate to large sample sizes, the authors argue that all these estimators have the same order of MSE. However, they differ in the contribution of bias to their MSE. The authors also consider their Pareto efficiency in squared bias versus variance space. All the above estimators are non-dominated (i.e., they lie on the Pareto frontier).

APPLICATION OF PIXE TO DETERMINATION OF ELEMENTS IN THE PLACENTA, MATERNAL BLOOD AND CORD BLOOD

1997 ◽  
Vol 07 (03n04) ◽  
pp. 211-217 ◽  
Author(s):  
Yoshito Watanabe ◽  
Yoshie Takubo ◽  
Masae Yukawa ◽  
Yoshikazu Nishimura ◽  
Hitoshi Imaseki ◽  
...  
Keyword(s):  
Cord Blood ◽  
Maternal Blood ◽  
Pixe Analysis ◽  
Blood Samples ◽  
Mean Values ◽  
The Mean ◽  
Standard Deviations ◽  
Homogenize Sample ◽  
Cu And Zn

PIXE technique was applied to the measurement of elements in the placenta, maternal blood and cord blood of human. The elements determined in these samples include Cl , K , Ca , Fe , Cu and Zn . The values obtained by PIXE were compared with those by ICP-AES to test the accuracy of the method. In placental samples, the mean values of K , Fe , Cu and Zn concentrations obtained by the two methods agree, while Ca concentration is lower in PIXE analysis. The values from PIXE, however, show larger variations resulting from inhomogeneity of the placental samples composed of various tissues different in histological functions. In the analysis of blood samples, the results of the two methods agree for Cl , K , Ca , Fe , Cu and Zn , although the standard deviations tend to be larger in PIXE. These results indicate that PIXE is a useful method for the determination of elements in placental and blood samples, although the preparation to homogenize sample is necessary to obtain accurate results.

Assay of Thiamine in Foods, Using Manual and Semiautomated Fluorometric and Microbiological Methods

1977 ◽  
Vol 60 (3) ◽  
pp. 522-527
Author(s):  
Phillip W Defibaugh ◽  
Jeffrey S Smith ◽  
Cora E Weeks
Keyword(s):  
Accurate Method ◽  
Official Method ◽  
Thiamine Hydrochloride ◽  
Fluorescent Method ◽  
Microbiological Methods ◽  
The Mean ◽  
Standard Deviations ◽  
Clam Tissue ◽  
Semiautomated Method

Abstract Three methods for the determination of thiamine in foods were evaluated for accuracy, recovery, and precision: a manual fluorescent method, a semiautomated fluorescent method, and a Lactobacillus viridescens microbiological assay. Thiamine in the samples was destroyed with clam tissue thiaminase; a known amount of thiamine hydrochloride was then added to the extract; and the thiamine recovery was determined. For 14 commercially processed food products analyzed by the manual and semiautomated methods, the mean per cent recovery values and standard deviations were 91.2±8.92 and 99.3±3.13%, respectively. Eight of these products were analyzed by all 3 methods. The mean per cent recoveries and standard deviations for these 8 samples were 90.7±8.97, 101±2.52, and 99.9± 1.03%, respectively, for the manual, semiautomated, and microbiological methods. The microbiological method with L. viridescens gave the best results for the products tested. The concentration of vitamin which can be measured is such that samples of low label declaration present no problems. The semiautomated method offers a rapid and accurate method of thiamine assay. The chemical reactions are identical to those of the official method. The major difference between the methods is in the sample cleanup. It is postulated that the low recovery observed for the manual method is due to incomplete elution of thiamine in the column purification step.

Spectrophotometric Determination of Pyrantel Tartrate in Swine Feeds by Method of Standard Additions: Collaborative Study

1978 ◽  
Vol 61 (2) ◽  
pp. 296-298
Author(s):  
Mark A Litchman
Keyword(s):  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Collaborative Study ◽  
Standard Additions ◽  
The Mean ◽  
Standard Deviations ◽  
Pyrantel Tartrate

Abstract The spectrophotometric method for pyrantel tartrate in swine feeds was collaboratively studied. Twenty-seven laboratories assayed feeds containing 0.0103, 0.0965, and 0.7902% pyrantel tartrate. Repeatability (σo) and reproducibility (ax) standard deviations were: σo = 0.00068%, σx = 0.00105% (10% of grand mean) for 0.0103% pyrantel tartrate level; σo = 0.0065%, σx = 0.0090% (10% of grand mean) for 0.0965% pyrantel tartrate level; and σo = 0.0415%, σx = 0.0743% (10% of grand mean) for 0.7902% pyrantel tartrate level. The mean theoretical recovery values for feeds containing 0.0103, 0.0965, and 0.7902% were 100, 97, and 96%, respectively. The method was adopted as official first action for feeds or concentrates containing 0.0106–0.8811% pyrantel tartrate.

Rates of GDP Referral of Complete Dentures to a Teaching Hospital

2000 ◽  
Vol os7 (2) ◽  
pp. 61-64
Author(s):  
David Lamb ◽  
Jennifer Walsh ◽  
Bryan Ellis
Keyword(s):  
Teaching Hospital ◽  
Referral Rate ◽  
Full Time ◽  
Complete Dentures ◽  
Full Time Equivalent ◽  
Referral Rates ◽  
Remedial Teaching ◽  
The Mean ◽  
Standard Deviations ◽  
Normally Distributed

Purpose of study To identify areas and sites of excessive referral of complete dentures by GDPs, allowing for factors which might distort referral rates. Methods Two hundred and six consecutive valid referrals of patients over the age of 50 years with complete dentures to a local dental teaching hospital and originating from the 29 Sheffield electoral wards were audited from the beginning of 1995 to the end of 1997. The referring practitioner and electoral ward were recorded. Results Referral rates were calculated according to the size of the 50+ population within each ward and were found to be normally distributed, following exclusion of two wards with much higher referral rates than normal (3.5 and 6 SDs [standard deviations] from the mean). After calculating mean numbers referred per full-time equivalent (FTE) GDP for all wards, practices and practitioners originating excessive numbers of referrals within a high-referring ward could be identified. Conclusion After taking into account factors which might permit a high referral rate to be acceptable, practices with inappropriately high referral rates can be identified and remedial teaching need pinpointed.

Gamma-Ray Spectroscopic Determination of Iodine-131 and Cesium-137 in Foods: Two Collaborative Studies

1989 ◽  
Vol 72 (4) ◽  
pp. 667-669
Author(s):  
Edmond J Baratta ◽  
David G Easterly
Keyword(s):  
Gamma Ray ◽  
Food Sample ◽  
Spectroscopic Determination ◽  
Collaborative Studies ◽  
Cesium 137 ◽  
Aoac Method ◽  
Iodine 131 ◽  
The Mean ◽  
Standard Deviations

Abstract The AOAC method for iodine-131, cesium-137, and barium-140 in milk by gamma-ray spectroscopy (48.025-48.029) was extended to include other foods for the radionuclides iodine-131 and cesium-137. Two collaborative studies were performed to validate this extension. In the first study, a food sample containing 119 pCi ,3,I/kg and 53 pCi 137Cs/kg was sent to each of 45 laboratories for triplicate analyses. For 25 responses, the mean of the reported values was 123.8 pCi/kg for iodine-131, and for 27 responses, the mean was 53.4 pCi/kg for cesium-137. Repeatability (within-laboratory) standard deviations (sr) for iodine-131 and cesium-137 were 4.6 and 3.7 pCi/kg, respectively. Reproducibility (among-laboratories) standard deviations (sR) for iodine-131 and cesium-137 were 12.1 and 6.0 pCi/kg, respectively. In the second study, a food sample containing 25 pCi 13,I/kg and 27 pCi 137Cs/kg was sent to each of 54 laboratories for triplicate analyses. For 21 responses, the mean of the reported values was 25.0 pCi/kg for iodine-131, and for 19 responses, the mean was 28.9 pCi/kg for cesium-137. sr Values were 4.0 and 1.6 pCi/kg for iodine-131 and cesium-137, respectively, and SR values were 5.0 and 2.8 pCi/kg, respectively. The method extension was adopted official first action.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

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