Analysis of a Uniformity Trial on Cassava

1968 ◽  
Vol 4 (2) ◽  
pp. 135-141
Author(s):  
Biyi Afonja
Keyword(s):  
Coefficient Of Variation ◽  
Unit Area ◽  
Plot Size ◽  
Methods Of Analysis ◽  
Area Basis ◽  
Very High

SummaryThe analysis of a uniformity trial on cassava is briefly discussed, mentioning possible effects of plant losses on the methods of analysis. Two methods of calculating comparable variances, on a per plant and per unit area basis, gave very high values for the index of heterogeneity, with a mean of 0·94. When the ratio of overall cost per plot to cost per unit area lies between one and two, an optimum plot size of between 16 and 32 plants is obtained. The comparable plot sizes would range from 192 to 385 sq. ft and give a coefficient of variation less than twenty.

scholarly journals Automating Uniformity Trials to Optimize Precision of Agronomic Field Trials

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1254
Author(s):  
Marcus Jones ◽  
Marin Harbur ◽  
Ken J. Moore
Keyword(s):  
Web Application ◽  
Unit Area ◽  
Field Trials ◽  
State University ◽  
Iowa State University ◽  
Plot Size ◽  
Maize Field ◽  
Process Uniformity ◽  
Field Plots ◽  
Uniformity Trials

Plot size has an important impact on variation among plots in agronomic field trials, but is rarely considered during the design process. Uniformity trials can inform a researcher about underlying variance, but are seldom used due to their laborious nature. The objective of this research was to describe variation in maize field trials among field plots of varying size and develop a tool to optimize field-trial design using uniformity-trial statistics. Six uniformity trials were conducted in 2015–2016 in conjunction with Iowa State University and WinField United. All six uniformity trials exhibited a negative asymptotic relationship between variance and plot size. Variance per unit area was reduced over 50% with plots 41.8 m2 in size and over 75% when using a plot size >111.5 m2 compared to a 13.9 m2 plot. Plot shape within a fixed plot size did not influence variance. The data illustrated fewer replicates were needed as plot size increased, since larger plots reduced variability. Use of a Shiny web application is demonstrated that allows a researcher to upload a yield map and consider uniformity-trial statistics to inform plot size and replicate decisions.

scholarly journals Analysis of the coefficient of variation in shear and tensile bond strength tests

2005 ◽  
Vol 13 (3) ◽  
pp. 243-246 ◽  
Author(s):  
Fábio Lourenço Romano ◽  
Gláucia Maria Bovi Ambrosano ◽  
Maria Beatriz Borges de Araújo Magnani ◽  
Darcy Flávio Nouer
Keyword(s):  
Coefficient Of Variation ◽  
Mean Value ◽  
Scientific Article ◽  
A Value ◽  
Statistical Analysis System ◽  
Strength Tests ◽  
Analysis System ◽  
Very High

The coefficient of variation is a dispersion measurement that does not depend on the unit scales, thus allowing the comparison of experimental results involving different variables. Its calculation is crucial for the adhesive experiments performed in laboratories because both precision and reliability can be verified. The aim of this study was to evaluate and to suggest a classification of the coefficient variation (CV) for in vitro experiments on shear and tensile strengths. The experiments were performed in laboratory by fifty international and national studies on adhesion materials. Statistical data allowing the estimation of the coefficient of variation was gathered from each scientific article since none of them had such a measurement previously calculated. Excel worksheet was used for organizing the data while the sample normality was tested by using Shapiro Wilk tests (alpha = 0.05) and the Statistical Analysis System software (SAS). A mean value of 6.11 (SD = 1.83) for the coefficient of variation was found by the data analysis and the data had a normal distribution (p>0.05). A range classification was proposed for the coefficient of variation from such data, that is, it should be considered low for a value lesser than 2.44; intermediate for a value between 2.44 and 7.94, high for a value between 7.94 and 9.78, and finally, very high for a value greater than 9.78. Such classification can be used as a guide for experiments on adhesion materials, thus making the planning easier as well as revealing precision and validity concerning the data.

Branched ears in wheat and yield determination

1972 ◽  
Vol 23 (4) ◽  
pp. 541 ◽  
Author(s):  
HM Rawson ◽  
KN Ruwali
Keyword(s):  
Unit Area ◽  
Field Conditions ◽  
Spikelet Number ◽  
Yield Production ◽  
Yield Determination ◽  
Very High

Differentiation of the branched ear of a semidwarf mutant wheat is described for plants grown under irrigated field conditions, and compared with cultivars bearing simple ears. With a very high spikelet number per ear (more than SO), and few grains per spikelet (a maximum of three), the branched ear offers a radically different concept for yield production. Yields per unit area of the current branched material were not as high as for Kalyan Sona, India's premier variety, but did exceed those for Late Mexico 120. Better yields could be expected if the random sterility of spikelets within the branched ear, first apparent early in spikelet differentiation, were reduced. However, individual fertile ears filled up to 128 grains weighing 4.8 g in the better plants.

Evaluation of two methods for assessing ascospore productivity of the apple scab pathogen, Venturia inaequalis

1981 ◽  
Vol 59 (6) ◽  
pp. 965-968
Author(s):  
C. C. Heye ◽  
J. H. Andrews ◽  
E. V. Nordheim
Keyword(s):  
Leaf Litter ◽  
Coefficient Of Variation ◽  
Unit Area ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Dry Weight ◽  
Weight Basis ◽  
Square Roots ◽  
Leaf Material ◽  
Normally Distributed

The standard water bubbler and a modified tower aspirator for quantifying ascospore productivity were compared. Samples, each consisting of 50 discs, were cut randomly from scab-infected McIntosh apple leaf litter in the spring and 18 samples were processed by each method. The square roots of hemocytometer counts adjusted for unit area or gram dry weight of leaf samples were found to be normally distributed. More spores were harvested from the same amount of leaf material with the bubbler than with the tower. The coefficient of variation for spore yields expressed on a per area or a per gram dry weight basis was smaller for the tower method than for the bubbler, although the values were not significantly different. Where detection of low ascospore productivity is not essential, the tower method is preferable in terms of ease, speed of operation, and the potential for electronic enumeration of harvested ascospores.

scholarly journals Skin friction of the wind on the Earth's surface

1916 ◽  
Vol 92 (637) ◽  
pp. 196-199 ◽  
Keyword(s):  
Flat Plate ◽  
Skin Friction ◽  
Solid Surface ◽  
Unit Area ◽  
Tangential Force ◽  
Mean Velocity ◽  
Small Surface ◽  
The Mean ◽  
General Velocity ◽  
Very High

The mechanism by means of which momentum is transmitted to a solid surface, in order that it may exert a drag on a fluid flowing past it, is at present understood only very imperfectly. It seems certain, however, that the law of dynamical similarity is applicable to skin friction; if therefore it were possible to measure the tangential force exerted by the wind as it blows over a large tract of land, it should be equal to the skin friction on a similar small surface when subjected to the action of the very high wind which would correspond with the same value of l V/ v . In reducing the tract of land to a similar small flat plate, the trees and houses would be reduced to a mere roughness on the plate. It is to be expected therefore that, if the skin friction on unit area of the earth's surface be expressed in the form F = kp Q 2 s , (1) Q s being the wind velocity near the surface and p the density of air, the constant k will be the same as the constant which would be found in the laboratory by experimenting with a small, slightly roughened plate, if a sufficiently high value of l V/ v , could be obtained. It should be noticed, however, that the velocity which should be compared with is the velocity close to the solid surface and not the general velocity of the air in the case of a flat plate, or the mean velocity over a cross section in the case of flow in a pipe.

scholarly journals Experimental planning for conducting experiments with cucumber

2020 ◽  
Vol 38 (2) ◽  
pp. 112-116
Author(s):  
Alessandro Dal’Col Lúcio ◽  
Darlei M Lambrecht ◽  
Bruno G Sari ◽  
Dionatan K Krysczun ◽  
Cassiane Ubessi
Keyword(s):  
Coefficient Of Variation ◽  
Experimental Error ◽  
Experimental Unit ◽  
Experimental Plot ◽  
Experimental Planning ◽  
Plot Size ◽  
Significant Difference ◽  
Experimental Variability ◽  
Fruit Mass ◽  
Fruit Diameter

ABSTRACT In order to be considered highly reliable (showing very accurate results), an experiment needs to be very well planned. Defining the experimental plot size and number of replicates is fundamental to control the experimental error at the beginning of the experiment. The aim of this study was to estimate the plot size and the number of replicates sufficient to perform experiments with Cucumis sativus. A uniformity trial was installed in the first week of January 2017. The spacing used was 0.3 m between plants and 1 m between rows, resulting in 12 plants in each of the 12 cultivation rows and each basic experimental unit was composed of one plant. The variables observed in 18 harvests were average fruit mass (MMF, in g), average fruit length (CMF, in cm) and average fruit diameter (DMF, in cm). The harvests were analyzed individually and grouped to reduce experimental variability. The number of replicates and the plot size were estimated using the method of maximum curvature of the coefficient of variation. The plot size and the number of replicates were influenced by the variability in the rows and between the harvests. We recommend plots consisting of four plants per cultivation row with six replicates for the minimum significant difference by Tukey’s test, expressed in 25% the means percentage.

scholarly journals Optimum Plot Size and Number of Replications with Short-day Onions for Yield, Seedstem Formation, Number of Doubles, and Incidence of Foliar Diseases

2003 ◽  
Vol 128 (3) ◽  
pp. 409-424 ◽  
Author(s):  
George E. Boyhan ◽  
David B. Langston ◽  
Albert C. Purvis ◽  
C. Randell Hill
Keyword(s):  
Coefficient Of Variation ◽  
Mean Difference ◽  
Basic Unit ◽  
Optimum Number ◽  
Chi Square ◽  
Yield Data ◽  
Plot Size ◽  
Maximum Curvature ◽  
Short Day ◽  
Southern Belle

Five different statistical methods were used to estimate optimum plot size and three different methods were used to estimate optimum number of replications with short-day onions (Allium cepa L.) for yield, seedstem formation (bolting), purple blotch and/or Stemphylium (PB/S), botrytis leaf blight (BLB), and bulb doubling with a basic plot size unit of 1.5 × 1.8 m (length × width). Methods included Bartlett's test for homogeneity of variance, computed lsd values, maximum curvature of coefficient of variation plotted against plot size, Hatheway's method for a true mean difference, and Cochran and Cox's method for detecting a percent mean difference. Bartlett's chi-square was better at determining optimum plot size with transformed count and percent data compared with yield data in these experiments. Optimum plot size for yield of five basic units (7.5 m length) and four replications is indicated using computed lsd values where the lsd is <5% of the average for that plot size, which was the case in both years of this study. Based on all the methods used for yield, a plot size of four to five basic units and three to five replications is appropriate. For seedstems using computed lsd values, an optimum plot size of four basic units (6 m length) and two replications is indicated. For PB/S two basic units (3 m length) plot size with four replications is indicated by computed lsd values. For BLB a plot size of four basic units (6 m length) and three replications is optimum based on computed lsd values. Optimum plot size and number of replications for estimating bulb doubling was four basic units (6 m length) and two replications with `Southern Belle', a cultivar with a high incidence of doubling using computed lsd values. With `Sweet Vidalia', a cultivar with low incidence of bulb doubling, a plot size of four basic units (6 m length) and five replications is recommended by computed lsd values. Visualizing maximum curvature between coefficient of variation and plot size suggests plot sizes of seven to eight basic units (10.5 to 12 m length) for yield, 10 basic units (15 m length) for seedstems, five basic units (7.5 m length) for PB/S and BLB, five basic units (7.5 m length) for `Southern Belle' doubling, and 10 basic units (15 m length) for `Sweet Vidalia' doubling. A number of plot size-replication combinations were optimum for the parameters tested with Hatheway's and Cochran and Cox's methods. Cochran and Cox's method generally indicated a smaller plot size and number of replications compared to Hatheway's method regardless of the parameter under consideration. Overall, both Hatheway's method and computed lsd values appear to give reasonable results regardless of data (i.e., yield, seedstems, diseases etc.) Finally, it should be noted that the size of the initial basic unit will have a strong influence on the appropriate plot size.

Contact Stiffness of New and Worn Surfaces

2005 ◽  
Author(s):  
A. Soom ◽  
C. I. Serpe
Keyword(s):  
Unit Area ◽  
Contact Stiffness ◽  
Measured Data ◽  
Wear Particles ◽  
Subsurface Cracks ◽  
Nominal Pressure ◽  
Resonance Frequencies ◽  
Area Basis ◽  
Steel Surfaces ◽  
Rough Surface Contact

The presence of surface texture/roughness on engineering surfaces results in contacts between surfaces being considerably more compliant than if the interfaces were smooth and flat. The inclusion of a local contact stiffness can be critical to the accurate analytical or computational modeling of mechanical contacts. We present measurements of contact stiffness for five pairs of freshly prepared and worn of steel surfaces. The wom surfaces variously contain surface glazes, oxide layers, subsurface cracks, inclusions and wear particles. Contact resonance frequencies between sample interfaces are measured at various applied pressures. With known modal masses, the contact stiffness is easily calculated and presented on a per unit area basis. For a given contact pair, the contact stiffness is nonlinear, increasing with nominal pressure and decreasing with increasing surface roughness. We compare these results with the Greenwood-Williamson (G-W) Theory of rough surface contact. The expected pressure and summit height dependencies are observed in the measured data. When there are wear particles within the contact, the stiffness is reduced when the underlying surfaces are very smooth. If the underlying surfaces are rough, the presence of wear particles have little effect on the contact stiffness.

scholarly journals Variability and Experimental Desing for Trials with Cucurbita pepo and Capsicum annuum

2017 ◽  
Vol 9 (11) ◽  
pp. 58
Author(s):  
Alessandro D. Lúcio ◽  
Daniel Santos ◽  
Tiago Olivoto
Keyword(s):  
Capsicum Annuum ◽  
Coefficient Of Variation ◽  
Cucurbita Pepo ◽  
Homogeneity Test ◽  
Plot Size ◽  
Homogeneity Of Variances ◽  
Randomized Design ◽  
Variance Homogeneity ◽  
Variability Data ◽  
Uniformity Trials

The variability within rows of cultivation may reduce the accuracy of vegetables trails; however, little is known about this variability in protected environments. This study aimed at to assess the variability in greenhouses cultivated with Cucurbita pepo and Capsicum annuum and to verify the effect of borders use and plot size in minimizing this variability. Data from two uniformity trials each crop were used. For statistical analysis, the total of productivity by plant was used, considering the plants arranged in parallel crop rows the lateral openings of the greenhouse and the same plants arranged in columns perpendicular to these openings. Different scenarios were designed by excluding rows and columns to generate the borders in different plot sizes. For each scenario, a variance homogeneity test was performed among the remaining rows and columns and the variance and coefficient of variation were calculated. There is variability among rows and columns in trials with C. pepo and C. annuum in greenhouses and the use of borders does not bring benefits in terms of reduction of the coefficient of variation or reduction of cases of variances heterogeneity among rows or columns. The use of a plot size greater than or equal to or two plants for trials with C. pepo and ten plants for trials with C. annuum provides homogeneity of variances among rows and columns enabling the use of the completely randomized design.

NUTRIENT DISTRIBUTION IN FOREST SOIL LEACHATES AFTER THINNING AND FERTILIZING DOUGLAS-FIR FOREST

1982 ◽  
Vol 62 (1) ◽  
pp. 197-208 ◽  
Author(s):  
P. C. PANG ◽  
K. McCULLOUGH
Keyword(s):  
Nitrogen Fertilization ◽  
Forest Floor ◽  
Unit Area ◽  
Nitrate Concentration ◽  
Nutrient Distribution ◽  
Plate Method ◽  
Area Basis ◽  
Forest Floor Leachates ◽  
Urea Fertilization ◽  
Nitrate Fertilization

The nutrients NH4+, NO3−, Ca2+, Mg2+ and K+ in leachates from immediately below the forest floor and from the mineral horizons at 10- and 30-cm depths were monitored with tension lysimeter plates held at 10 ± 1.0 kPa. Experimental plot treatments were thinning, fertilizing with nitrogenous fertilizers (448 kg N∙ha−1), and both. Concentrations (mg∙L−1) of these nutrients in the forest floor leachates increased immediately following nitrogen fertilization, but returned to near those of untreated levels about 5–10 mo later. Concentrations fluctuated at 10- and 30-cm depths in the mineral horizons. With urea fertilization, the increases in concentrations of nutrients were primarily associated with the forest floor. Nitrate concentration of 200 mg N∙L−1 in the forest floor leachate 5 mo after urea fertilization compared to 0.1–0.5 mg N∙L−1 of the untreated, indicated that nitrification had taken place. With ammonium nitrate fertilization, substantially higher concentrations of NO3−, Ca2+, Mg2+, and K+ were detected at 10- and 30-cm depths compared with urea fertilization. Thinning, when combined with urea fertilization, enhanced the movement of nutrients to greater depth in the soil profile. On a unit area basis (kg∙ha−1) the leaching of nutrients from soil horizons could be overestimated by the tension lysimeter plate method, as these plates do not only draw soil water from directly above.

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