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Questions tagged [coefficient-of-variation]

A measure of dispersion expressed relative to the mean, used for positive variables. Equals the standard deviation divided by the mean.

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4
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7k views

What does a squared coefficient of variation signify?

The coefficient of variation is defined as the ratio of S.D to mean, a dimensionless number which on multiplication by 100 gives the percentage of dispersion with mean. But when we square this ...
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96 views

What is the proper method for calculating the Coefficient of Variation of a rate?

I have been asked to evaluate the variation between movement rates of fish within different systems (rates are in km/day). I have between 25-100 samples in each system. I understand that when ...
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188 views

Comparing variation of two datasets of dimensionless quantities

I have a biological dataset in which we measured two dimensionless quantities $x$ and $y$. Let $X = \{x_1,\dots,x_N\}$ and $Y = \{y_1,\dots, y_N\}$ be the vectors holding this data. I want to argue ...
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2k views

Cut off values of the coefficient of variation in determining whether to include/exclude a sample

I'm fairly new to statistics and could use some advice. I have 70 blood serum samples that have had metabolite concentrations tested twice. (Same blood draw, different test dates). I calculated the ...
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851 views

Statistical comparison of data dispersion between two groups

I was trying to find a suitable way to compare the relative data dispersion between two groups and also to investigate if they are statistically significant. During the last weeks, I have searched a ...
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1answer
60 views

What is the most meaningful method to test whether two versions of the same measuring tool are producing consistent results?

I have got myself confused as to what method will best tell me whether the results from two measuring devices are producing the same results. Basically the subject will wear two devices while ...
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15 views

Gamma GLMM Dispersion, Random Effects, and CoV (lme4)

So I know that in glm(), with the Gamma family, one can get the dispersion parameter through the MASS package with gamma.dispersion() or can even look at the summary output as a quick estimate. How ...
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224 views

ANOVA on time series Data

I’ve been dealing with this problem for quite a time. I’m running an experiment with plants growing them with Compost A and Compost B. I’ve been measuring the pH each day at the same time and keeping ...
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15 views

significance testing of unequality of coefficient of variation in multiple samples

I'm performing a study on inter-doctor variation. For that, I'm studying a diagnostic instrument that has around 100 items that all have to be rated. Some are dichotomous, some ordinal. Several ...
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16 views

Model the CV of response variable as a function of CV of predictors

Suppose I have a big county that has 10 farms. In the county, the planting of a crop could happen between March to April. I collected for a given year, the planting date of a crop across the 10 farms ...
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14 views

Distribution of extremes of measurments considering repeated measures

I'm working with measurements for a large sample set and need to quantify the expected extremes. The measurements obviously have some degree of random noise simply in the measurement itself (for the ...
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99 views

Can I compare the average coefficients of variation?

I have two datasets. The first shows a populations choices for mode of transport (3 modes) in 6 different areas. The second shows the same populations responses to concerning attributes (13 ...
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43 views

Generalised coefficient of variation?

Consider the CV for a given random variable $X$: $$ CV_X = \frac{\sigma_X}{\mu_X}$$ Now, say I also have random variable $Y$. Let us define: $$ CV_{X,Y}= \sqrt{\frac{\text{Cov}(X,Y)}{\mu_X \mu_Y}} $...
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18 views

dependency of the deviation to the measurement level: how to test normality?

A machine measures the height of some plants. In the context of industrial quality procedures, we repeat the same measurement Hi 10 times and expect the ...
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13 views

How to compare two distribution where each point is not from a independent sample

columns are samples and rows are genes. There are two groups. I calculated coefficient of variance (CV) for each group so for each gene there are two CV one for group A and one for group B. I ...
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13 views

Is there a statistic or metric that measures variation (or deviation from mean) in a time-dependent manner?

I am evaluating two time series. One has a larger Coefficient of Variation (CV) than the other. But I have also noticed that one of the time series has longer consecutive deviations from the mean. ...
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502 views

Is a gamma distribution adapted when the coefficient of variation is roughly the same across observations?

Each observation is a distribution of values. Computing the mean $\mu_i$ and standard deviation $\sigma_i$ for each observation $i$ showed that the coefficient of variation (CV) is roughly constant ...
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641 views

Alternative for coefficient of variation due to negative observations

I have several measurements of trees over time (different vegetation indexes). Each measurement is in a different scale, some also include negative values (e.g. NDVI). I need to compare the ...
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44 views

Different sample size calculations for variable and 1-variable

I am trying to use coefficients of variations ($CV$) to calculate sample size necessary to detect a difference of means ($\mu_0$ vs. $\mu_1$) for a variable that takes on values $x_i \in [0,1]$. I ...
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43 views

How do I calculate the cv for observation errors from a time series of actual values and a time series of values with observation error?

I have a time series of actual values. I also have a time series consisting of values with observation error. Assuming that the observation errors are normally distributed, independent of one ...
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542 views

Interpreting standard deviation ratio (is std deviation ratio equal to coefficient of variation?)

I am new in this area. I apologizes if my question is silly. I need to include the homogeneity and heterogeneity of variance as one of the factor in my robustness study.Therefore, i saw this phrase. ...
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169 views

Coefficient of variation for % increase

I was reading about the coefficient of variation and it seems that it can only be computed for ratios (non-negative values). I have a list of values which indicate the % increase in a particular ...
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72 views

Estimating prevalence of an effect in a RCT study using the overlapping coefficient (and does chocolate make your acne worse?)

I'm trying to tease out prevalence of effects seen from controlled studies, e.g. what % of people would expect to see a higher acne lesion count if consuming 6 oz of cocoa / day? The average effect is ...
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386 views

How do I compare multiple coefficients of variation?

I have an experiment organized as follows: N repeated measures were done for each of M different conditions (each one having a different mean value) The experiment was done P times, each time using a ...
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503 views

How to calculate relative error of a random variable?

This maybe a naive question, but I found two ways to calculate the relative error, one is common and another is from the papers I read. Assume that the exact number is $n$, and the estimated number ...
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374 views

distribution of sample variance or sample coefficient of variation under gamma parent distribution

I am looking for anything related to the distribution of the sample variance or sample coefficient of variation (or joint with sample mean or conditional on sample mean) when the parent distribution ...
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212 views

Significance of Co-efficient of Variation

Is there a formula that is able to determine whether the difference between two co-efficients of variation is significant or if not is there a specific heuristic used to determine significance (i.e. ...
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2k views

Alternative to coefficient of variation (CV)/relative standard error as a measure of estimate's reliability/stability

I am seeking a statistic measuring an estimate's reliability or stability as an alternative to the coefficient of variation (CV), also known as the relative standard error. The CV is the standard ...
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13 views

Test for Statistical Differences Among Coefficients of Variation (using R)?

I have two datasets, and I wish to determine the statistical difference between two groups. I am comparing a visual plant injury scoring system to a remotely-sensed scale, and the coefficient of ...
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1answer
11 views

coefficient of variation and genes highly expressed

I am a biologist, with very little knowledges of statistics. I am looking for highly variable genes from a data set. I have calculated the coefficient of variation of the expressed genes of my dataset ...
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21 views

Total sum of squares or coefficient of variation

I have two sets of histology data for the same set of patients, each with two samples. Both are made based on fraction stained cells relative to total number of cells (stained+unstained), but their ...
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15 views

Methods to quantity the applicability of an regression to a larger population

Simple question I believe, but I am not as sharp on my stats as i would like to be. I have 66 items with a calculated value associated with them, due to data restraints I was only able to find a "...
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11 views

How should I compare variability across repeated measures in a single trial vs variability across measurements across repeated trials?

I have collected some data from different subjects in 2 different ways. In the first way, each subject performed one long trial, I segmented the data captured and and calculated a variable value for ...
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24 views

Coefficient of variation and residual standard deviation

From my knowledge, coefficient of variation and residual standard deviation are highly correlated. Such that if we find a significant change in one, we will find a significant change in the other. In ...
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24 views

is coefficient of variation better measure of highly variable features?

I am trying find highly variable features (genes in my data) for downward consensus clustering analysis. I have used variation, median absolute deviation and coefficient of variation (CV) for finding ...
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39 views

Calculating the probability of exceeding a given return

I have calculated the return of an investment with cost and benefit data as 80% with a 4.6% coefficient of variation. However, I need to carry the analysis further by calculation the probability of ...
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185 views

comparing two sets of coefficient of variation values

I have two sets of coefficient of variations (cv): ste1 = c(cv1, cv2, ..., cv15) set2 = c(cv1, cv2, ..., cv15) how can I compare set1 with set2? which test should I apply? I know that if I want to ...
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867 views

Inconsistency between coefficient of variation (CV) and geometric CV

Geometric CV seems to be an appropriate measure for log-normalized data. Also, according to the discussions mentioned in theorems 1 and 2 of here, it seems to me that CV and geometric CV are both ...
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47 views

How to compare annotations by two groups?

I have two groups of test persons that manually created multiple annotations for different underlying, unknown values (each person created multiple annotations). I'd like to find a statistical test ...
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19 views

Coefficient of Variation across Prediction Intervals

I've run into an odd problem that I have a simple answer to but would like to know if there's something deeper to it. I have a data set with 7 observations, each with 2 variables (X,Y). I then run a ...
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57 views

Handle data with high variation

I'm analyzing som product data that shows sells over the past day, week and month. In some cases I have a very high number but in most cases this number is quite low, and this is affecting quite a lot ...
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552 views

Relative Standard Deviation (RSD) of more than 100%

Relative standard deviation (RSD) is defined as: $$ RSD = \frac{100 \times s}{\overline{x}} $$ where $s$ is the standard deviation and $\overline{x}$ is the mean. How should a RSD of 170% for a ...
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193 views

How to compare coefficients of variation for lognormal data?

I want to compare the variability of two log-normal samples. They are being summarized as Coefficient of variations (CVs) and I want to test if one sample's CV is different from the other's. To ...
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0answers
72 views

Including the variation within a sample when comparing between samples

I want to include the variation within a sample when analysing the variation between samples. Say I have sample A, B, C. Sample A was analysed three times with the values: 2398, 2383, 2411 Sample B: ...
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1answer
69 views

Coefficient of variation for shipping

I want to understand if the coefficient of variation ($c_v$) is the right calculation to use for measuring how far off I am when shipping goods to customers. The date I want to ship to customers is ...
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1answer
103 views

Alternative to a coefficient of variation

I am currently collecting data 4x per week with a fencing athlete. She jumps with each foot on a separate force plate, so we can see asymmetries in force curves. We noticed that whenever she is more ...
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0answers
48 views

Which statistical method can I use to see if there is a correlation between data sets with different size?

For my thesis I want to compare the 3 different test results. If the results are more than 5, samples are failed. And I want to show if these tests are similar behaviour (if there is a correlation ...
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0answers
537 views

Measure of dispersion for dataset with zero mean

I'm testing a machine learning algorithm which, until now used coefficient of variation in order to relative measure dispersion among different attributes in a given dataset. Now that I need to test ...
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0answers
349 views

Is there any guide line to select a right coefficient of variation?

I faced an estimation problem of compute the mean of a random variable (rv) $X$. What I know is the coefficient of variation of this rv, namely its standard deviation divided by its mean: $$c_{v}(X) = ...
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0answers
714 views

Use coefficient of variation (CV) to compare precision testing results

Can I just use coefficient of variation (CV) to compare my results and make conclusion from it? I need to write up results from running 2 controls (Precision testing-intra assay/inter assay and ...