A Statistical Method for Evaluating the Reproducibility of Age Determination

1982 ◽  
Vol 39 (8) ◽  
pp. 1208-1210 ◽  
Author(s):  
William Y. B. Chang
Keyword(s):  
Statistical Method ◽  
Fish Species ◽  
Coefficient Of Variation ◽  
Age Determination ◽  
Statistical Test ◽  
Absolute Difference ◽  
Percent Error ◽  
Percent Agreement ◽  
Coefficients Of Variation ◽  
Variation Index

The coefficients of variation and the index of precision provide a statistical test of reproducibility of aging between readers. Because the coefficients of variation and the index of precision incorporate the averaged year-class of a fish species, they are free from the shortcoming of the percent agreement method. Because variance is a better estimator than absolute difference, the coefficient of variation is a stronger estimator than the index of average percent error in providing a test statistic.Key words: age determination, coefficients of variation, index of precision, average percent error, percent agreement

scholarly journals Reproducibility of age determination by scale and vertebra in pontic shad (Alosa pontica Eichwald, 1838), from the Danube

2009 ◽  
Vol 61 (2) ◽  
pp. 337-341 ◽  
Author(s):  
Zeljka Visnjic-Jeftic ◽  
Mirjana Lenhardt ◽  
I. Navodaru ◽  
A. Hegedis ◽  
Z. Gacic ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Age Determination ◽  
Danube River ◽  
Experienced Reader ◽  
Percent Error ◽  
The Danube River ◽  
Iron Gate

Specimens of Pontic shad (Alosa pontica Eichwald, 1838) were collected during April and May of 2006 in the Danube River (rkm 863) just downstream of the Iron Gate (Djerdap) II dam. Twenty-eight scales and 30 vertebrae were prepared and given to five interpreters with fish aging experience of from 3 to 30 years and with shad aging experience of from 0 to 12 years. Interpreters with experience in shad age determination showed lower values for the index of average percent error (IAPE) and an index of coefficient of variation (ICV). In regard to within-interpreter reproducibility, no significant differences were found between scale and vertebrae as structure for age determination. The most experienced reader showed the lowest value for IAPE, while the least experienced reader showed the highest value for IAPE. The results of this work indicate that experience in age determination by particular structure had more impact on age determination precision than specificity of structure, scale or vertebra. More work is needed on adopting standard protocols that must include some sort of common interaction between responsible age readers.

A Method for Comparing the Precision of a Set of Age Determinations

1981 ◽  
Vol 38 (8) ◽  
pp. 982-983 ◽  
Author(s):  
R. J. Beamish ◽  
D. A. Fournier
Keyword(s):  
Age Determination ◽  
Percent Error ◽  
Percent Agreement ◽  
Age Determinations

An index of average percent error is a better estimate of the precision of age determinations than the conventional percent agreement method because it is not independent of the age of a species.Key words: age determination, aging errors

scholarly journals Directly ageing the Caribbean spiny lobster, Panulirus argus with validated band counts from gastric mill ossicles

2018 ◽  
Vol 76 (2) ◽  
pp. 442-451 ◽  
Author(s):  
Gaya Gnanalingam ◽  
Mark J Butler ◽  
Thomas R Matthews ◽  
Emily Hutchinson ◽  
Raouf Kilada
Keyword(s):  
Spiny Lobster ◽  
Age Determination ◽  
Florida Keys ◽  
Panulirus Argus ◽  
Gastric Mill ◽  
Coefficients Of Variation ◽  
The Caribbean ◽  
First Time ◽  
Reader Experience

Abstract In crustaceans, ecdysis was long believed to result in the loss and replacement of all calcified structures, precluding the use of conventional ageing methods. However, the discovery of bands in the gastric ossicles of several crustaceans with some correlation with age suggests that direct age estimation may be possible. We applied this method to a tropical spiny lobster, Panulirus argus, one of the most iconic and economically valuable species in the Caribbean. The presence of growth bands was investigated using wild lobsters of unknown age and was validated with captive reared lobsters of known age (1.5–10 years) from the Florida Keys, Florida (USA). Bands were consistently identified in ptero- and zygo-cardiac ossicles of the gastric mill and did not appear to be associated with moulting. Validation with known age animals confirms that bands form annually. Counts between independent readers were reproducible with coefficients of variation ranging from 11% to 26% depending on reader experience and the structure used. This study demonstrates, for the first time, that direct age determination of P. argus is possible.

Glycohaemoglobin: Comparison of 12 Analytical Methods, Applied to Lyophilized Haemolysates by 101 Laboratories in an External Quality Assurance Programme

1993 ◽  
Vol 30 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Cas W Weykamp ◽  
Theo J Penders ◽  
Frits A J Muskiet ◽  
Willem van der Slik
Keyword(s):  
Quality Assurance ◽  
Acetic Acid ◽  
Coefficient Of Variation ◽  
External Quality Assurance ◽  
External Quality ◽  
Quality Assurance Programme ◽  
Coefficients Of Variation ◽  
Two Samples ◽  
The Mean ◽  
Edta Blood

Stable lyophilized ethylenediaminetetra-acetic acid (EDTA)-blood haemolysates were applied in an external quality assurance programme (SKZL, The Netherlands) for glycohaemoglobin assays in 101 laboratories using 12 methods. The mean intralaboratory day-to-day coefficient of variation (CV), calculated from the assay of 12 unidentified pairs over a period of 1 year, was 5·2% (range: 0·2–28·7). Forty-seven per cent of laboratories did not meet the criterion of CV < 5%, whereas 68% did not meet the clinically more desirable 3·3–3·6%. Linearity, as derived from the analysis of five combinations of two haemolysates with low and high glycohaemoglobin percentages over 6 months, was excellent (mean correlation coefficient 0·9953; range: 0·9188–0·9999). Analysis of two samples with high and low glycohaemoglobin percentages gave mean interlaboratory coefficients of variation of 10% for one method performed by several laboratories and 22% for all methods performed by all laboratories. It is concluded that the majority of laboratories do not meet the clinically desirable intralaboratory precision and that an unacceptably high interlaboratory precision exists.

scholarly journals Methodological and physiological variability within the ventilatory response to hypoxia in humans

2000 ◽  
Vol 88 (5) ◽  
pp. 1924-1932 ◽  
Author(s):  
Shu Zhang ◽  
Peter A. Robbins
Keyword(s):  
Coefficient Of Variation ◽  
Ventilatory Response ◽  
Systematic Variation ◽  
Hypoxic Ventilatory Response ◽  
Mean Values ◽  
Careful Choice ◽  
Physiological Variability ◽  
Coefficients Of Variation ◽  
Ventilatory Response To Hypoxia ◽  
Over Time

Measurement of the acute hypoxic ventilatory response (AHVR) requires careful choice of the hypoxic stimulus. If the stimulus is too brief, the response may be incomplete; if the stimulus is too long, hypoxic ventilatory depression may ensue. The purpose of this study was to compare three different techniques for assessing AHVR, using different hypoxic stimuli, and also to examine the between-day variability in AHVR. Ten subjects were studied, each on six different occasions, which were ≥1 wk apart. On each occasion, AHVR was assessed using three different protocols: 1) protocol SW, which uses square waves of hypoxia; 2) protocol IS, which uses incremental steps of hypoxia; and 3) protocol RB, which simulates an isocapnic rebreathing test. Mean values for hypoxic sensitivity were 1.02 ± 0.48, 1.15 ± 0.55, and 0.93 ± 0.60 (SD) l ⋅ min− 1 ⋅ %− 1for protocols SW, IS, and RB, respectively. These differed significantly ( P < 0.01). The coefficients of variation for measurement of AHVR were 20, 23, and 36% for the three protocols, respectively. These were not significantly different. There was a significant physiological variation in AHVR ( F 50,100 = 3.9, P < 0.001), with a coefficient of variation of 26%. We conclude that there was relatively little systematic variation between the three protocols but that AHVR varies physiologically over time.

scholarly journals Variability Associated with Testing Shelled Corn for Fumonisin

1998 ◽  
Vol 81 (6) ◽  
pp. 1162-1168 ◽  
Author(s):  
Thomas B Whitaker ◽  
Mary W Trucksess ◽  
Anders S Johansson ◽  
Francis G Geesbrecht ◽  
Winston M Hagler ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Sample Preparation ◽  
Coefficient Of Variation ◽  
Variance Component ◽  
Test Procedure ◽  
Functional Relationships ◽  
Similar Test ◽  
Coefficients Of Variation ◽  
Order Of Magnitude

Abstract Variances associated with sampling, sample preparation, and analytical steps of a test procedure that measures fumonisin in shelled corn were estimated. The variance associated with each step of the test procedure increases with fumonisin concentration. Functional relationships between variance and fumonisin concentration were estimated by regression analysis. For each variance component, functional relationships were independent of fumonisin type (total, B1, B2, and B3 fumonisins). At 2 ppm, coefficients of variation associated with sampling (1.1 kg sample), sample preparation (Romer mill and 25 g subsample), and analysis are 16.6,9.1, and 9.7%, respectively. The coefficient of variation associated with the total fumonisin test procedure was 45% and is about the same order of magnitude as that for measuring aflatoxin in shelled corn with a similar test procedure.

Interlaboratory Comparison of Analyses for Heavy Metals in Clam Tissue

1986 ◽  
Vol 69 (5) ◽  
pp. 863-868
Author(s):  
Marilyn R Hendzel ◽  
Bruce W Fallis ◽  
Brigitte G E Demarch
Keyword(s):  
Heavy Metals ◽  
Coefficient Of Variation ◽  
Interlaboratory Comparison ◽  
Interlaboratory Study ◽  
Oyster Tissue ◽  
Coefficients Of Variation ◽  
Freeze Dried ◽  
Lead Levels ◽  
Clam Tissue ◽  
Cu And Zn

Abstract Results are reported for an interlaboratory study conducted to assess the reproducibility of analyses for lead, copper, cadmium, and zinc. The 10 participating laboratories analyzed 2 samples of freeze-dried clam tissue and 1 disguised sample of NBS Oyster Tissue. Interlaboratory variations were observed for all metals, although the methods yielded reproducible data for Cu and Zn with average interlaboratory coefficients of variation of 15 and 11%, respectively. The performance of methods used for Cd and, more so, for Pb was less than satisfactory. Cadmium levels in the 3 samples ranged from about 0.7 to 3.7 ppm with an average interlaboratory coefficient of variation (CV) of 24%. Lead levels in the 3 samples were about 0.5 ppm with an interlaboratory CVof 68%. Some laboratories' results were consistently high or low but data were insufficient to relate these trends to one particular variable. Results from this study were compared with 5 other studies reported in the literature since 1980. Coefficients of variation from all studies were comparable for samples with similar metal concentrations

Evaluation of Tumor Measurements in Oncology: Use of Film-Based and Electronic Techniques

2000 ◽  
Vol 18 (10) ◽  
pp. 2179-2184 ◽  
Author(s):  
Lawrence H. Schwartz ◽  
Michelle S. Ginsberg ◽  
Douglas DeCorato ◽  
Lawrence N. Rothenberg ◽  
Steven Einstein ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Interobserver Variability ◽  
Tumor Therapy ◽  
Measurement Techniques ◽  
Cross Product ◽  
Ct Images ◽  
Coefficients Of Variation ◽  
Significant Difference ◽  
The Cross ◽  
Tumor Measurements

PURPOSE: To evaluate the variability in bidimensional computed tomography (CT) measurements obtained of actual tumors and of tumor phantoms by use of three measurement techniques: hand-held calipers on film, electronic calipers on a workstation, and an autocontour technique on a workstation. MATERIALS AND METHODS: Three radiologists measured 45 actual tumors (in the lung, liver, and lymph nodes) on CT images, using each of the three techniques. Bidimensional measurements were recorded, and their cross-products calculated. The coefficient of variation was calculated to assess interobserver variability. CT images of 48 phantoms were measured by three radiologists with each of the techniques. In addition to the coefficient of variation, the differences between the cross-product measurements of tumor phantoms themselves and the measurements obtained with each of the techniques were calculated. RESULTS: The differences between the coefficients of variation were statistically significantly different for the autocontour technique, compared with the other techniques, both for actual tumors and for tumor phantoms. There was no statistically significant difference in the coefficient of variation between measurements obtained with hand-held calipers and electronic calipers. The cross-products for tumor phantoms were 12% less than the actual cross-product when calipers on film were used, 11% less using electronic calipers, and 1% greater using the autocontour technique. CONCLUSION: Tumor size is obtained more accurately and consistently between readers using an automated autocontour technique than between those using hand-held or electronic calipers. This finding has substantial implications for monitoring tumor therapy in an individual patient, as well as for evaluating the effectiveness of new therapies under development.

Microbiological Assay of Oxytetracycline in Feed: Manual Turbidimetric Assay and Plate Assay

1973 ◽  
Vol 56 (1) ◽  
pp. 23-30
Author(s):  
Hussein S Ragheb ◽  
Anne M Cummings ◽  
Barbara M Browning
Keyword(s):  
Coefficient Of Variation ◽  
Microbiological Assay ◽  
Plate Method ◽  
Turbidimetric Method ◽  
Plate Assay ◽  
Coefficients Of Variation ◽  
Aoac Method ◽  
Turbidimetric Assay ◽  
Turbidimetric Analysis ◽  
Feed Samples

Abstract The useful range for manual turbidimetric analysis of Oxytetracycline (OTC), using K. pneumoniae, was between 0.04 and 0.08 μg/ml in the assay tubes. Laboratory-prepared feeds containing 43.5 and 86.5 g OTC.HCl/ton gave 90–98% recovery by the turbidimetric method and 104–116% by the AOAC method, 38.211–38.213. The coefficients of variation were 9.2–13.0 and 10.2–12.8%, respectively. Feeds containing 50 and 100 g OTC.HCl and neomyein sulfate/ton gave 77% of theory when analyzed turbidimetrically and 95% of theory by the plate method. The coefficient of variation for the turbidimetric method was about 16%, indicating unsatisfactory precision. At 200 g/ton theoretical concentration of each antibiotic, both methods agreed. Commercial premixes and finished feed samples gave almost the same results by both methods. The main advantage of the turbidimetric method over the plate assay is that results can be obtained the same day of analysis.

scholarly journals Improved Small Sample Inference on the Ratio of Two Coefficients of Variation of Two Independent Lognormal Distributions

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
A. Wong ◽  
L. Jiang
Keyword(s):  
Medical Research ◽  
Coefficient Of Variation ◽  
Lognormal Distribution ◽  
Special Interest ◽  
Small Sample ◽  
Simulation Studies ◽  
Lognormal Distributions ◽  
Coefficients Of Variation ◽  
Ratio Approach ◽  
Modeling Data

Without the ability to use research tools and procedures that yield consistent measurements, researchers would be unable to draw conclusions, formulate theories, or make claims about generalizability of their results. In statistics, the coefficient of variation is commonly used as the index of reliability of measurements. Thus, comparing coefficients of variation is of special interest. Moreover, the lognormal distribution has been frequently used for modeling data from many fields such as health and medical research. In this paper, we proposed a simulated Bartlett corrected likelihood ratio approach to obtain inference concerning the ratio of two coefficients of variation for lognormal distribution. Simulation studies show that the proposed method is extremely accurate even when the sample size is small.

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