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Questions tagged [standard-deviation]

Standard deviation is the square root of the variance of a random variable, an estimator thereof, or a similar measure of the spread of a batch of data.

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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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Compute standard deviation of accuracy

The following code represents my problem : ...
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Qualtrics and Epi Info yield different Standard Deviation values?

Uncertain if this is the correct place to post this, but I'll give it a shot. I'm a Master's Student working with a small (n=25 respondents) data set. I originally entered my surveys into Qualtrics. ...
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Name for Standard Deviation over possible range (1-255)?

I have RGB brightness values over a possible range of 1-255. I am already computing Coefficient of Variation, but since my domain is strictly limited, I am interested in seeing a measure of how spread ...
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Mean Absolute Deviation and sum of independent random variables

Consider the sum of 2 independent random variables $P$ and $Q$ with unknown distributions. It is known that the variance of the sum of the variables is the sum of the variances. Is there any ...
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what is the difference between Standard error of the means vs Sampling error?

I am confused after learning about the different terms. I understood Standard error of the means to be the Standard Deviation of the sample means, whilst Sampling error is the Standard Deviation ...
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How to evaluate the degree to which survey results are scattered

Let's say I have a number of numeric answers from a group of people and I need to decide whether the group agrees on the question or not. I can imagine doing this by calculating standard deviation of ...
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Geometric mean and geometric standard deviation

When summarizing normalized data (for example, percentage data), one must use the geometric mean instead of the arithmetic mean. Thus, instead of using the arithmetic standard deviation, one shall use ...
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Method of comparing the evenness of data sets [closed]

I need to compare and rank multiple sets of data for their evenness, flatness or in other words average deviation from their relative mean. I'm intending for each set to have a value which would be ...
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Calculate Percent Change after running Paired Samples T-test

I have two measurements pre and post. I ran a paired samples t-test to determine if a statistically significant difference exists between pre and post. I would like to report the Percent difference ...
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overall variance of different time signals

I have two sensors mounted on two appliances and they measure a variable in the time domain every 1 second. Now for the course of 1 hour, I want to make only one error bar that contains both signals....
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Lottery with known EV and standard deviation. Probablity of positive ROI after x trials?

Lottery with the following payout table: **Payout** **Frequency** 0x 0.59992 1x 0.34992 5x 0.04982 1000x 0.00035 ...
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Question about the meaning of Variance/Standard Deviation [duplicate]

I know that these two functions have statistical significance, but I'm finding it hard to grasp any intuition about them. I understand that in their own way they represent some type of 'average' ...
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Breaking Down Standard Deviation Into Smaller Units

I have calculated my standard deviation in winnings by session of playing poker, with each session being an average of X hours. Since everything in the poker world is discussed in terms of standard ...
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Standard error of conflated and uncorrelated events

If we have n, uncorrelated random events, the standard error of the mean would be : $\frac{\sigma}{\sqrt n}$ Now lets think in a little different way. If each event contains a pair of variables which ...
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Retrieving instantaneous information from average quantities

I have a very large vector containing instantaneous information on a quantity on the timescale of microseconds. I also have another vector of the same quantity containing the 10 minute max, 10 minute ...
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How to calculate summary limits of agreement?

I have made a forest plot including multiple studies assessing agreement using Bland and Altman plots between values measured by two different methods. However, most studies only reported mean ...
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Outliers odd behaviour

I got a sample of data. I applied a linear correction to it and then I calculate again the mean and standard deviation. The mean and the standard deviation before and after the correction are almost ...
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Expected value for max weight of two stones (given independent uncertainty in each) [duplicate]

If I have two stones A and B with estimated weights (and associated uncertainties) of A=100 +/- 5kg B=102 +/- 2kg Is there any formula (or good approximation) to compute the expected value of ...
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How to check covariate is balanced?

I try to check if the covariate is balanced by computing the absolute pooled standardized difference, but I don't know how I could get the sample variance for my treated and control covariate? any ...
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Calculating annualized volatility from yearly returns

I have the yearly_return in percentage of some stocks and I would like to get the annualized volatil- ity. Yet when I tried to apply sd(yearly_return) it returned ...
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For binomial success / fail data, how to calculate if the time since last success is out of the normal range

Struggling to figure this out. I have data sets that are essentially ObjectId, Date, Pass/Fail (1/0) The data is normally daily. What I want to figure out is IF the number of days since the last ...
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Something that bothers my intuitive thinking [closed]

Here is an interesting situation I came along recently: Turnover January: 5 million February: 6 million Cost of goods sold (CoGS) January: 2 million February: 4 million If we look at the relative ...
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Combined Variance of two groups with different sample sizes [duplicate]

I have the mean and standard deviation for Male and Female groups in a study, I'm trying to get the combined mean and standard deviation. The two groups have different N's. I can get the weighted ...
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how to spot weekly versus monthly prices in an area

I have price rents for properties distributed over the country for the last 2 years (a total amount of 2M properties). The problem is that some of the prices are monthly and other weekly. To spot the ...
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Given a list of standard deviation values, how do I find the overall standard deviation of the whole set?

I have a program which takes a set of images and collects various types of information about the colours within each image. One of the things it collects is the mean of each RGB colour value (in a ...
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1answer
39 views

Calculating the probability that the standard deviation is above or below a certain value

I'm given $n$ samples from a random number generator that produces normally distributed values. Can I calculate the probability that the standard deviation that the RNG uses is $\sigma > \sigma_{...
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Are these confidence intervals calculated correctly?

Is the 1SD calculation correct in this image? Instead of 16% for 1SD on each side of the mean, they have 34%. SD2 and SD3 are correct. SD2=100-95 = 5%. Divide by 2 = 2.5%. and same for SD3 = 99.7% (....
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Obtain SE or 95%CI from 95% limits-of-agreement (Bland and Altman)

I am updating a forest plot with studies reporting the agreement between blood values extracted from two different sampling sites (from arteries and veins). I use review manager 5.3 (Cochrane) which ...
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How to reproduce this algorithm?

I am trying to reproduce one of the algorithms presented in the following paper: Rapid Assessment of Annual Deforestation in the Brazilian Amazon Using MODIS Data The authors provide five different ...
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Estimate for the error of an error?

Searching through Wikipedia and StackExchange I managed to understand that, for a set of $N$ normally distributed values, the unbiased variance $Var[s^2]$ of the unbiased variance $s^2$ of the ...
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1answer
41 views

Does standard distance follow the 68-95-99.7 rule?

I'm wanting to do a simple standard distance demonstration for my students in R, but I've come across a conundrum. When I simulate the creation of 10,000 points in a spatial normal distribution, ...
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174 views

Why do we use squared deviations to compute the SD, given that it amplifies the effect of outliers? [duplicate]

Suppose I have the following hypothetical data: One thousand times value 15 (i.e., 15 occurs 1000 times) and a single outlier value - 115 (i.e., 115 occurs just once - an outlier) Thus the mean is: $...
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How to take into consideration errors in Mann-Whitney test?

I have 2 independent samples (groups), each group contains 10 experimental values of variable T and their standard deviations (errors). I need to do intergroup statistical analysis, i.e. to elucidate ...
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can I work out *the* standard deviation from a value given as “+/- 1 standard deviation”

I'm confronted by a table of values: 17.1 (16.6) 18.0 (9.5) 38.1 (22.5) 30.6 (16.7) In the left-hand column we have some mean values. I’m told that the values ...
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Variance of the mean in case of a quadratic trend

Please allow me to use Python code to put my question across. Suppose we want to model a variable using either a linear or a quadratic trend: ...
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Uncertainty from equation involving fitted parameters [closed]

I want to estimate the uncertainty of a calculation which involves a quantity from a fitted mathematical model. More specifically, the end calculation would be something like: P = x / A_tot where I ...
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division of of values with standard deviations

I need to normalize results from my experiment to the control in that experiment. I have two repeats from each condition (test and control), and each has a standard deviation. When dividing to ...
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Can a difference between statistical deviations be interpreted as a statistical deviation?

I have a cross-table of three variables (2x2x3 design) and I obtained 7 outcome variables for each condition. Since each condition is not a group of participants but a group of models sample size is ...
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Which correction do I need to get a measurement uncertainty from the sample standard deviation?

I'm an experimental physicist who mainly needs statistics for the calculation of measurement uncertainties and confidence intervals. Since my results are usually normally distributed, I simply take $N$...
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Standard Error of a formula

If I do have 100 samples of irrigated plants (labeled from 1 to 100) and 100 samples of non-irrigated plants (during 5 days) (labeled to 101 to 200) from a drought tolerant specie and 100 samples ...
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How to calculate the error of percentages

Is it correct to calculate the standard deviation of percentages/proportions as you would for four numbers (i.e. non-percentages)? Thanks for your help @user2974951 @whuber and @asdf. Yes, you're ...
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Standard error of the population from a bootstrapped distribution

I would like to compute the Std. Error (SE) of some statistic (lets call it a). Given than the distribution of a is usually not normal, I performed a bootstrap. I am not sure how to compute the SE ...
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Why do we round up the Standard Deviation when it rounds regularly to 0? [closed]

Why do we round up the Standard Deviation when it rounds regularly to 0? For instance, if our SD is 0.02, we round it up to 0.1, but if it is 0.06, we keep it at 0.06. Can someone please explain? ...
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Does 1 divided by standard deviation tell us anything? [duplicate]

(1/standard deviation) I've seen someone use this and I would like to ask for clarity on this because the intuition of it isn't immediately obvious. Standard deviation tells us how dispersed the ...
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23 views

Standard deviation in multimodal data

I have a dataset, 90% of observations are unimodal normal (with couple of outliers per feature), 10% are mixture of normals, components have the same standard deviations. Data contains outliers => ...
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34 views

Statistical test for replicate measurements with mean and standard deviation

I am having some trouble trying to find the right statistical test for my experiment. It is a flow cytometry experiment with many replicates and I am comparing normal and disease states. I get a ...
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1answer
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Get better confidence interval by drawing multiple samples

Imagine that I have population of size N and I draw a sample of size n from which I compute a proportion $\hat{p}$ of a categorical variable. And I want to get a confidence interval of 95%. So I ...
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Does this mean my model is useless?

Long story short, I have a random forest I've created. It's mean absolute error is .209 for the test set. The (scaled) standard deviation of the y column is .201 (for all the y column data, not just ...
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1answer
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different formula to calculate standard deviation

I have a naive question. I have list a a = [1, 2, 3, 6] . mymean = sum(a)/len(a) To ...