Firing Variability Is Higher than Deduced from the Empirical Coefficient of Variation

2011 ◽  
Vol 23 (8) ◽  
pp. 1944-1966 ◽  
Author(s):  
Susanne Ditlevsen ◽  
Petr Lansky
Keyword(s):  
Experimental Data ◽  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Estimation Methods ◽  
Interspike Intervals ◽  
Estimation Errors ◽  
Empirical Standard Deviation ◽  
Receptor Neurons ◽  
The Mean ◽  
Empirical Standard

A convenient and often used summary measure to quantify the firing variability in neurons is the coefficient of variation (CV), defined as the standard deviation divided by the mean. It is therefore important to find an estimator that gives reliable results from experimental data, that is, the estimator should be unbiased and have low estimation variance. When the CV is evaluated in the standard way (empirical standard deviation of interspike intervals divided by their average), then the estimator is biased, underestimating the true CV, especially if the distribution of the interspike intervals is positively skewed. Moreover, the estimator has a large variance for commonly used distributions. The aim of this letter is to quantify the bias and propose alternative estimation methods. If the distribution is assumed known or can be determined from data, parametric estimators are proposed, which not only remove the bias but also decrease the estimation errors. If no distribution is assumed and the data are very positively skewed, we propose to correct the standard estimator. When defining the corrected estimator, we simply use that it is more stable to work on the log scale for positively skewed distributions. The estimators are evaluated through simulations and applied to experimental data from olfactory receptor neurons in rats.

Awareness, Benefits, and Services: Lecturers’ Perceived Towards The Application of ISO 9001: 2008 at University

2018 ◽  
Vol 2 (2) ◽  
pp. 108
Author(s):  
Ahmad Syukri ◽  
Nisaul Fadillah
Keyword(s):  
Standard Deviation ◽  
Significant Relationship ◽  
Iso 9001 ◽  
Survey Method ◽  
Full Time ◽  
Research Findings ◽  
Empirical Standard Deviation ◽  
The Mean ◽  
Empirical Standard

Abstract: The State Islamic Institute Sulthan Thaha Saifuddin (IAIN STS) Jambi has been applying ISO 9001; 2008 since February 2013. One of previous research findings was the resistance regarding the ISO standards and the certification process. This study was to examine the problem through conducting lecturers’ perception towards ISO 9001; 2008 at IAIN STS Jambi in terms of their awareness, benefits and services. Respondents were lecturers of IAIN STS Jambi as many as 122 people from 4 faculties. The research employed a quantitative survey method that uses a likert-scale questionnaire and analysed with descriptive statistic. The findings show that lecturers’ perception on the application of TQM ISO 9001: 2008 in IAIN STS Jambi included in the group of moderate to high. The mean empirical data (x = 47,30) was higher than the average hypothetical (μ = 42). This indicates that the perception of lecturers on the application of ISO in IAIN STS Jambi is high (positive). Empirical standard deviation (s = 9,910) was higher than the hypothetical standard deviation (σ = 9:33). This shows that the perception of lecturers on the application of ISO 9001: 2008 at IAIN STS Jambi has a high variation. Meanwhile, gender variable has a significant relationship between the perception of ISO 9001: 2008 on improving the quality of teaching. Employment status (fulltime civil employer or non-full-time civil employer) have a significant relationship between the perception of ISO 9001; 2008 for quality of services and quality of coordination.

A Proof for Rhiel's Range Estimator of the Coefficient of Variation for Skewed Distributions

2007 ◽  
Vol 100 (1) ◽  
pp. 208-210 ◽  
Author(s):  
G. Steven Rhiel
Keyword(s):  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Research Study ◽  
Skewed Distributions ◽  
The Mean ◽  
Standard Deviations

In this research study is proof that the coefficient of variation ( CVhigh-low) calculated from the highest and lowest values in a set of data is applicable to specific skewed distributions with varying means and standard deviations. Earlier Rhiel provided values for dn, the standardized mean range, and an, an adjustment for bias in the range estimator of μ. These values are used in estimating the coefficient of variation from the range for skewed distributions. The dn and an values were specified for specific skewed distributions with a fixed mean and standard deviation. In this proof it is shown that the dn and an values are applicable for the specific skewed distributions when the mean and standard deviation can take on differing values. This will give the researcher confidence in using this statistic for skewed distributions regardless of the mean and standard deviation.

scholarly journals Properties of the Standard Deviation that are Rarely Mentioned in Classrooms

2016 ◽  
Vol 38 (3) ◽  
Author(s):  
Mohammad Fraiwan Al-Saleh ◽  
Adil Eltayeb Yousif
Keyword(s):  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Sample Variance ◽  
Mean Absolute Deviation ◽  
Hidden Information ◽  
Absolute Deviation ◽  
Sample Mean ◽  
The Mean ◽  
Vague Concept ◽  
Chebyshev's Inequality

Unlike the mean, the standard deviation ¾ is a vague concept. In this paper, several properties of ¾ are highlighted. These properties include the minimum and the maximum of ¾, its relationship to the mean absolute deviation and the range of the data, its role in Chebyshev’s inequality and the coefficient of variation. The hidden information in the formula itself is extracted. The confusion about the denominator of the sample variance being n ¡ 1 is also addressed. Some properties of the sample mean and varianceof normal data are carefully explained. Pointing out these and other properties in classrooms may have significant effects on the understanding and the retention of the concept.

Correction for Rhiel's Theory for the Range Estimator of the Coefficient of Variation for Skewed Distributions

2010 ◽  
Vol 106 (1) ◽  
pp. 93-94
Author(s):  
G. Steven Rhiel
Keyword(s):  
Standard Deviation ◽  
Correction Factor ◽  
Coefficient Of Variation ◽  
Unbiased Estimate ◽  
Correction Factors ◽  
Skewed Distributions ◽  
The Mean

In 2007, Rhiel presented a technique to estimate the coefficient of variation from the range when sampling from skewed distributions. To provide an unbiased estimate, a correction factor ( an) for the mean was included. Numerical correction factors for a number of skewed distributions were provided. In a follow-up paper, he provided a proof he claimed showed the correction factor was independent of the mean and standard deviation, making the factors useful as these parameters vary; however, that proof did not establish independence. Herein is a proof which establishes the independence.

scholarly journals The precision of temporal judgement: milliseconds, many minutes, and beyond

2009 ◽  
Vol 364 (1525) ◽  
pp. 1897-1905 ◽  
Author(s):  
P.A. Lewis ◽  
R.C. Miall
Keyword(s):  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Human Subjects ◽  
Short Interval ◽  
Time Measurement ◽  
Scalar Property ◽  
Timing Mechanisms ◽  
Timing Data ◽  
The Mean ◽  
Different Levels

The principle that the standard deviation of estimates scales with the mean estimate, commonly known as the scalar property, is one of the most broadly accepted fundamentals of interval timing. This property is measured using the coefficient of variation (CV) calculated as the ratio between the standard deviation and the mean. In 1997, John Gibbon suggested that different time measurement mechanisms may have different levels of absolute precision, and would therefore be associated with different CVs. Here, we test this proposal by examining the CVs produced by human subjects timing a broad range of intervals (68 ms to 16.7 min). Our data reveal no evidence for multiple mechanisms, but instead show a continuous logarithmic decrease in CV as timed intervals increase. This finding joins other recent reports in demonstrating a systematic violation of the scalar property in timing data. Interestingly, the estimated CV of circadian judgements fits onto the regression of decreasing CV, suggesting a link between short interval and circadian timing mechanisms.

Cosine Tuning Minimizes Motor Errors

2002 ◽  
Vol 14 (6) ◽  
pp. 1233-1260 ◽  
Author(s):  
Emanuel Todorov
Keyword(s):  
Experimental Data ◽  
Standard Deviation ◽  
Motor System ◽  
Force Production ◽  
Noise Model ◽  
Motor Processing ◽  
Natural Choice ◽  
Activation Profile ◽  
Redundant Actuators ◽  
The Mean

Cosine tuning is ubiquitous in the motor system, yet a satisfying explanation of its origin is lacking. Here we argue that cosine tuning minimizes expected errors in force production, which makes it a natural choice for activating muscles and neurons in the final stages of motor processing. Our results are based on the empirically observed scaling of neuromotor noise, whose standard deviation is a linear function of the mean. Such scaling predicts a reduction of net force errors when redundant actuators pull in the same direction. We confirm this prediction by comparing forces produced with one versus two hands and generalize it across directions. Under the resulting neuromotor noise model, we prove that the optimal activation profile is a (possibly truncated) cosine—for arbitrary dimensionality of the workspace, distribution of force directions, correlated or uncorrelated noise, with or without a separate cocontraction command. The model predicts a negative force bias, truncated cosine tuning at low muscle cocontraction levels, and misalignment of preferred directions and lines of action for nonuniform muscle distributions. All predictions are supported by experimental data.

ASSESSMENT OF PURITY OF PROPOLIS ON OKSITETRATSIKLIN'S PRESENCE BY HPLC METHOD

2021 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
A.M. Smirnov ◽  
◽  
R.Т. Klochko ◽  
S.N. Lugansky ◽  
V.P. Galimova ◽  
...  
Keyword(s):  
Experimental Data ◽  
Standard Deviation ◽  
Hplc Method ◽  
Practical Application ◽  
Operating Modes ◽  
The Mean

The technique of detection of the residues of oxytetracycline in propolis by means of chromatography HPLC is fulfilled. Operating modes of technique are fulfilled, the experimental data testimonial of reliability of use of this method for broad practical application in system of working or arbitration control of safety of bee propolis are obtained. Sensitivity of technique on oxytetracycline makes 8-12 mkg/kg. The mean of the determination is 90%, the standard deviation is 4%.

Distribution of Movement Time in a Target-Aiming Task

1976 ◽  
Vol 43 (2) ◽  
pp. 507-513 ◽  
Author(s):  
Tarald O. Kvålseth
Keyword(s):  
Experimental Data ◽  
Standard Deviation ◽  
Normal Distribution ◽  
Linear Model ◽  
Movement Time ◽  
Arm Movements ◽  
Order Linear ◽  
First Order ◽  
Index Of Difficulty ◽  
The Mean

Various characteristics of the distribution of movement time were analyzed for a task involving serial and rotary arm movements aimed at a target. For experimental data generated from five Ss, (a) the distribution tended to be unimodal and more peaked than a normal distribution, (b) the skewness of the distribution was predominantly positive and (c) the standard deviation, in addition to the mean, of movement time was significantly affected by the complexity of the task as measured by Fitts' index of difficulty, while the skewness and the kurtosis were not. For the average results for the Ss, a first-order linear model with the standard deviation of movement time as the dependent variable and Fitts' index as the independent one explained 67% of the variation in standard deviation as compared to 98% of the variation in mean movement time accounted for by the Fitts' index.

scholarly journals Climate resources analysis for use of planning in crop production and rainfall water management in the central highlands of Ethiopia, the case of Bishoftu district, Oromia region

2010 ◽  
Vol 7 (3) ◽  
pp. 3733-3763 ◽  
Author(s):  
F. Yemenu ◽  
D. Chemeda
Keyword(s):  
Markov Chain ◽  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Rainy Season ◽  
Growing Season ◽  
Entire Study ◽  
Dry Spell ◽  
The Mean ◽  
Central Highlands ◽  
Main Rainy Season

Abstract. Agricultural practices and water resources management in the central highlands of Ethiopia is highly dependant and associated with climatic resources and their pattern and hence wise use of those resources is a priority for the region. Accordingly, a study was conducted to asses and critically quantity the climate resources of the central high lands of Ethiop, Bishoftu district. Thirty three years of weather record data has been used for the work. The onset, duration and end of the growing seasons were defined and quantified based on FAO and Reddy models while the dry and wet spell distributions and the drought events were calculated using the Markov chain models and the standardized precipitation index (SPI) respectively. The results revealed that the mean onset of the main (Kiremt) growing season was found to occur during the second meteorological decade and ended during the end of September. Similarly, though unreliable and only few occurred during the entire study period, the mean onset of the shorter (Belg) season was found to occur during the beginning of the first decade of April. The length of the growing season during the main rainy season, (Kiremt,) ranged from 112 to 144 days with a standard deviation of 9.6 days and coefficient of variation of 7.5%. However, the mean growing length during the Belg season was found to be 22.4 days with a standard deviation of 27 days and coefficient of variation of 122%. The results of analysis obtained both from the Markov Chain and Reddy models indicated higher probabilities of dry spell occurrences during the shorter season (Belg) but the occurrences of the same in the main rainy season (Kiremt) was very minimal. Like wise, the SPI model detected some drought events ranging from mild to severe classes in both seasons based on one a month time scale analysis. A considerable attention of maximizing crop harvest during the main rainy season is practically important.

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