homogeneity of variance
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Author(s):  
Mohd Yunus Shukor

When it comes to finding the best fit of nonlinear curves to acceptable models, linear regression with least squares is the most effective technique. Because residuals (the difference between observed and predicted data) must follow a normal distribution and the data must be free of outliers and uniform variance, statistical tests are used to identify the most appropriate model for a given situation (homoscedasticity). If all of these characteristics are satisfied, the system is said to be robust. In parametric nonlinear regression, one of the numerous assumptions is that the within-group variances of the groups are all the same, which is one of several assumptions (exhibit homoscedasticity). If the variances vary from one another (show heteroscedasticity), then the model is not statistically competent to describe the data as a whole. Data on the detection of Vibrio cholerae DNA with polystyrene-coacrylic acid composite nanospheres as modelled using the nonlinear four-parameter logistic (4PL) regression was preliminary check for homogeneity of variance using the Bartlett’s and Levene’s tests. It was found that the critical value of 2 was 28.869, according to Bartlett's test findings. Excel's CHIDIST function yielded a probability of 0.389 (not significant), suggesting that the variances of the residuals did not change significantly. The p-value for Levenes's test was 0.917, indicating that there were no distinct changes between the residual variances meaning that the use of the 4-PL model in fitting the data was adequate statistically.


ENTOMON ◽  
2021 ◽  
Vol 46 (4) ◽  
pp. 305-312
Author(s):  
S. Sahina ◽  
M.I. Zahir Hussain ◽  
R. Balasubramanain

A study was undertaken on the ovicidal and larval repellent activity of Tagetes erecta leaf and flower extracts on Rhipicephalus sanguineus (Latreille, 1806), an important tick species in the world from an economic and medical point of view. Ethanol and methanol extracted plant products tested against the eggs and larvae of R. sanguineus indicated that the ethanol extract of flower had maximum ovicidal activity (86.1%), followed by the ethanol extract of leaf (75%) at 25 mg ml-1 concentration. In all analyses, the homogeneity of variance was significant. The probit analysis clearly indicated that the ethanol extract of the flower has a higher ability to kill the eggs. In the case of larval repellency tested, both extracts of leaf showed the highest repellency (83%) at 2.5 mg ml-1. Significant tick repellency (> 90%) was found in both methanol and ethanol extracts of flower at 2.5 mg ml-1. GC-MS analysis of extracts revealed the presence of bioactive insecticidal compounds such as yangambin, cyclohexane and neophytadine.


2021 ◽  
Vol 8 (6) ◽  
pp. 979-983
Author(s):  
Meshal Harbi Odah

Financial time series are defined by their fluctuations, which are characterized by instability or uncertainty, implying that there are periods of volatility followed by periods of relative calm. Therefore, time series analysis requires homogeneity of variance. In this paper, some models used in time series analysis have been studied and applied. Comparison between Autoregressive Moving Average (ARMA) and Generalized Autoregressive Conditionally Heteroscedastic (GARCH) models to identify the efficient model through (MAE, MASE) measures to determine the best forecasting model is studied. The findings show that the models of Generalised Autoregressive Conditional Heteroscedastic are more efficient in forecasting time series of financial. In addition, the GARCH model (1,1) is the best to forecasting exchange rate.


2021 ◽  
Vol 39 (11) ◽  
Author(s):  
Adel Kashkool ◽  
Roa'a Mohammed Kadhim ◽  
Hasan Yahya Baqer

Oil-producing countries depend on oil revenues mainly to finance their public budgets and thus influence Directly on the public spending process and according to economic logic, the financial abundance leads to an increase in public spending. And that's what A detailed event in the Iraqi economy during the years of explosive budgets for the years 2012 and 2013 due to high prices Oil has reached unprecedented levels. The process of public spending did not focus on the investment side, which would The economy and the various sectors developed, as they focused only on recreational and consumer activities, which led to the loss of an opportunity Financial abundance and the lack of impediment to the advancement of the Iraqi economy. The research focuses on the variables of oil revenues and public spending and the close relationship that exists between them. The quarterly data was taken, which is more accurate than the annual data, and the sample consisted of 66. Watching from 2004 to 2019. The series was subjected to silence tests for the two mentioned variables, and it was found that they did not They settle at the level and are stabilized when taking the first difference and after doing the graph test and proceeding to complete the rest the exams . An autoregressive ARDL method was selected, and the appropriate model was selected. For each of the oil revenues and public spending, and regarding the integration parameter, it was negative and significant, as well as the limits test that He indicated the possibility of long-term interpretation that the coefficients of the variables were  significant, as the percentages of significance ranged between 1%, 5%, and . 10% of the sequence. The model was subjected to a dimensional test, which confirmed the integrity of the model from standard problems and the statistical as a test of autocorrelation of the residuals and the result was not significant. As well as the test for instability of homogeneity of variance, which is The other is immaterial.


2021 ◽  
Vol 13 (3) ◽  
pp. 1995-2002
Author(s):  
Siti Irawahyuni ◽  
Pratiwi Pujiastuti ◽  
Aninditya Sri Nugraheni

Snowball Throwing-style cooperative learning has been shown to impact primary school students' academic performance positively. This type of research is quasi-experimental. Documentation and testing methods are used to collect data. Before hypothesis testing using t-tests, the data analysis technique used descriptive analysis and prerequisite analysis tests such as initial ability, normality and homogeneity of variance tests. According to the findings, Indonesian subjects taught using the cooperative learning model of the snowball throwing type had an average score of 19,750, and those taught using the expository learning model had an average score of 17,578. The t-test yielded tcount = 3.114 and ttable = 2.026 as the final results. This means that Indonesian primary school students learn differently in classes taught using the snowball-throwing cooperative learning model and classes taught using expository learning models, according to the t-test results. Snowball Throwing type cooperative learning is more influential than expository learning on Indonesian for elementary school subject learning outcomes according to the results of t-tests.


2021 ◽  
Vol 1 (11) ◽  
pp. 735-748
Author(s):  
Hermansyah Hermansyah ◽  
Nurhendi Nurhendi

The purpose of this research is to see how flash cards influence the students' English vocabulary mastery. The researchers of this research used quantitative research methods with posttest only control design of true experimental design. The random sampling method was employed in this research's sampling. The data collected in this research was put to the test (multiple choice test). The researchers of this research gave different treatments for the experimental and control groups. The treatment for the experimental group was learning English with flash card media and the treatment for the control group was learning English conventionally. After the two sample groups were given different treatment, the two sample groups were each given a posttest with an instrument consisting of 20 multiple-choice questions with 4 alternative answer choices that had been tested beforehand and validated empirically. Analysis of research data is descriptive and inferential, which inferentially uses the t test, by first testing the assumptions of data normality and homogeneity of variance. The results showed that flash cards had an influence on students' English vocabulary mastery. Therefore, it can be said that this research has proved that there was a significant result of using Flash Cards towards children's English vocabulary mastery.


2021 ◽  
Vol 2 ◽  
Author(s):  
Mia Maor-Cohen ◽  
Shirli Bar-David ◽  
Amit Dolev ◽  
Oded Berger-Tal ◽  
David Saltz ◽  
...  

Translocated animals typically find themselves in a novel environment in which they must establish a home range in a manner that will maximize their fitness. We hypothesized that the initial establishment of a home range is followed by adjustments expressed as home range shifting, and occurs as familiarity with the landscape increases, until the home range is stabilized. We studied the process of home range shifting in 42 female Persian fallow deer (Dama mesopotamica) reintroduced into the Galilee, Israel over a period of 2–5 years. We used changes in the degree of home range overlap between consecutive years as an indicator of stabilization. We then compared how the mean percent cover of the key vegetation types (woodland, scrubland and open pastures) differed between the areas abandoned in the first year's home range and the areas added to the last year's home range relative to the first (using a weighted paired t-test). We also compared the distribution (using χ2 test of independence and Levene's test for homogeneity of variance) of %cover of the 3 vegetation types between the first and last year's home range. The average home range overlap increased over the 5 years following the first release. During the first-year post release, deer avoided open pastures and preferred woodland. In later years deer increase in the % open pastures (weighted t-test: p < 0.001) and decreased the % woodland cover (weighted t-test: p = 0.07) by abandoning areas with little open pasture and steeper terrain and moving into areas with more open pasture and moderate terrain. Variance of the cover types across individuals increased with time. We conclude that the home ranges of the reintroduced deer stabilized with time. The changes in vegetation and slope are driven by time-dependent changing needs reflecting a tradeoff between safety (refuge) and foraging. Our findings suggest that using the initially established home range to determine species preferences can create a misleading picture of what the optimal home range of the species really is. Individual variation in term of preferences can take a few years to be expressed due to the initial high-risk perceived by individuals in a novel environment.


Author(s):  
C. K. Beneragama ◽  
K. Goto ◽  
V. N. Kodithuwakkuge

Aims: The research aimed to investigate the shade response of E. gracilis Klebs while making the irradiance a crucial factor for photosynthesis based physiological activities and its applicability for industrial level culture conditions. Study Design: Euglena was cultured at three different light intensities of 30, 90, and 210 mol m-2s-1 photoautotrophically and axenically in modified Cramer-Meyer medium at 25 ˚C as batch cultures. Methodology: The photosynthesis O2 evaluation of Euglena cultures was measured under exponential (EP), transitional (TP), and stationary phases (SP). The light compensation point (LCP), light saturation point (LSP), and dark respiration rate (DRR) were obtained. Cell volume and cell number in each culture were measured simultaneously. Cells were collected and obtained dry mass (DM) after drying aliquots at 80˚C. Specific growth rate (SGR) and relative growth rate (RGR) were calculated. Tests for homogeneity of variance were performed on all parameters and LSDs were used for the mean separation. Results: In the TP, the lowest LCP was achieved in the higher light culture. The values of both the DRR and the LSP were the same as in EP. The DRR, LCP and LSP are lower in lower PFD cultures and decreased with increasing cell titers. The cellular growth levels were lower in lower light culture and decreased as each culture grew. Cellular DM was maintained constant in the EP, where SGR almost equaled RGR. In the EP, SGR was maintained constant in each culture, SGR displayed a saturation phenomenon. In the later TP, SGR became equal to RGR and all the cultures revealed constant DM. Conclusion: Euglena photoautotrophic cultures can tolerate low light intensities. With the SGR and RGR behavior under the shade conditions, they can maintain the constant photosynthesis rate and constant dry matter level.


2021 ◽  
Vol 20 (2) ◽  
pp. 81
Author(s):  
Kus Hendarto ◽  
Yohanes Cipta Ginting ◽  
Agus Karyanto ◽  
Virginia Chintya Amanda

This study aims to determine the effect of NPK dosage, types of complementary fertilizers and their interactions on the growth and production of chilies pepper.  This research was conducted in Sukabanjar Village, Gedong Tataan, Pesawaran Regency from July-December 2020.  The experimental design used in this study was a two-factor randomized block design (RBD), namely the dose of NPK fertilizer and the type of complementary fertilizer (4 × 2) with 3 replications.  Each plot consisted of 8 plants so that there were 192 plants.  The first factor was NPK Mutiara fertilizer dose (16:16:16)(N) with N0:0 g/plant, N1:10 g/plant, N2:20 g/plant and N3:30 g/plant.  The second factor is the type of complementary fertilizer (P) with P1 Plant Catalyst and P2 Gandasil D. Homogeneity of variance was tested by Bartlett test, additivity was tested by Tukey test. Then it was continued with analysist of variance and with the Least Significant Difference test (LSD) at the 5% level. Treatment of NPK fertilizer dosage significantly increases growth and yield.  The interaction between the NPK dosage of 20g/plant and type of complementary fertilizers gave highest plant height (95.58 cm). The best  combination was NPK dosage of 20 g/plant and Plant Catalyst fertilizer that gave highest yield (753,17 g/plant equivalent 15.06 ton/ha at population 20,000 plant/ha.Keywords : Chili pepper, complimentary fertilizer, growth, NPK, yield


2021 ◽  
Vol 20 (2) ◽  
pp. 104
Author(s):  
Hidayat Pujisiswanto ◽  
Yayuk Nurmiaty ◽  
Nanik Sriyani ◽  
Annisa Efrima

Adjuvant is an ingredient added in a formulation to increase the effectiveness of lerak fruit in inhibiting weeds. This study aims to determine the type of adjuvant in lerak fruit extract that can increase the inhibition of germination of Fimbristylis miliacea and to determine the type of adjuvant in lerak fruit extract that is most effective in inhibiting the germination of F. miliacea. The research was conducted from December 2019 to March 2020 in the Weed Laboratory, Faculty of Agriculture, University of Lampung. This study used a Completely Randomized Design (CRD) to determine the type of adjuvant given to lerak fruit extract on F. miliacea germination with 4 replications. The treatments consisted of lerak fruit extract, lerak fruit extract + VCO adjuvant, lerak fruit extract + KAO adjuvant, lerak fruit extract + Polysorbate 80 adjuvant, and control. The Bartlett test was used to test the homogeneity of variance, if the assumptions of the analysis of variance were met, then the mean value of the treatment was continued with the Least Significant Difference (LSD) test at the 5% level. The results showed that adjuvants and without adjuvants added to lerak fruit extract at a concentration of 50% (500 g/l) were able to suppress the percentage of germination and the speed of germination of Fimbristylis miliace seeds.Keywords: adjuvants, lerak fruit extract, Fimbristylis miliacea, weed


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