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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R prints column, but does not save it to global environment

I am a bit confused here and not able to find a good answer. I have a dataframe that I am trying to aggregate: ...
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Why doesn't Stdev take absolute value of x- xbar? [duplicate]

Newbie here. Curious why standard deviation subtracts x from xbar and then ^2's them instead of skipping hte squaring/square-rooting and instead takes the ABS value of each x-xbar Thanks mods
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How to calculate the “cumulative” standard deviation

I have gridded spatial data. The data is 30-year averaged climate data and has units of mm/yr and an associated standard deviation for that grid cell. For example, a grid cell has a value of X mm/yr, ...
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Sample size for standard deviation estimation

There are lots of videos/sources talking about how to define a sample size in order to estimate the population's mean, given a standard deviation. But no one talks about the sample size needed to ...
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What is Forecast Standard Deviation and is there a formula for it?

I'm familiar with statistics and errors for measurement such as Mean Absolute Percentage Error, MAE, MSE, MAD, RMSE, SMAPE (plus others) and their mathematical formulas but so far I've not found a ...
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Calculating a weighted mean and weighted SD from multiple mean/SD/different sample sizes?

QUESTION EDITED: I have 10 different patients, who have undergone heart procedures and we have collected some measurements of cardiac electrical activity from the same region of all ten hearts. Due to ...
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Population standard deviation in meta analysis

Suppose that data from different experiments all come from the same normal distribution (fixed effect). Is it possible to estimate the population standard deviation in a meta-analysis? I have found ...
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Calculate standard deviation for grayscale imagenet pixel values with rotation matrix and regular imagenet standard deviation

I want to train some models to work with grayscale images, which e.g. is useful for microscope applications. Therefore I want to train my model on graysale imagenet, using the pytorch grayscale ...
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How to calculate sd change for metaanalysis? [closed]

For my metaanalysis, I have a paper which only has delta change of mean after intervention and its associated CI ie Δmean(x,y) As an example, it looks like this : -5(3.2,4.0) I would like to know how ...
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Statistical tests for within and between individual variance

I am looking to determine the between individual variance and the within individual variance for the subjects in my data set. My data is setup like below: [1]: https://i.stack.imgur.com/dAqXq.png I am ...
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Statistical Interpretation of 2 data set measures

I was adviced to post here (initialy post on physics exchange but I am going to remove it). I have two independant experiments have measured $\tau_{1},\sigma_{1}$ and $\tau_{2},\sigma_{2}$ with $\...
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How to calculate standard deviation of residuals in a Bayesian logistic regression model fit with brms?

I fit a binary logistic regression model with brms as follows: ...
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Bootstrapping OLS coefficient variance different results than Python Statsmodels

I wanted to test some basic OLS things in python with a sample dataset. One thing I wanted to test was just getting a bootstrap estimate of the variance of the model's coefficients. Here is the setup ...
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How do i calculate if the difference between two advertisement campaigns is significant?

My brother has asked me if I can evaluate if his advertisement campaigns yield significantly different results. It was a couple of years ago I dealt with these kinds of problems, so would appreciate ...
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t-test or z-test: assume normality or s≈σ?

Let's say I have a large sample ($n>30$) with mean $\bar{X}$ and standard deviation $S$. I can calculate only: $T=\frac{\bar{X}-\mu}{S/\sqrt{n}}$. If I want to use t-test for a hypothesis, then I ...
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I need help finding mean and standard deviation

Given that 80% of the values are less than 140 and 75% is less than 135. Distribution is a normal distribution. Find the mean and standard deviation. Anyone can help to find and explaining a solution? ...
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doubts on what to consider when doing statistical tests

I am having some existential doubts on statistics; maybe someone here can help me clear out the dust. I've trying get answers from literature, but I found most reads quite vague, which still leaves me ...
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Age recognition accuracy calculation

I have several measurements for age recognition for a group of subjects, for whom I have the ground truth values (their true ages). I would like to measure the accuracy of age recognition (e.g., ...
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Is it really appropriate to say “standard deviation” is variation or dispersion

Question I have been struggling to convince myself that SD (standard deviation) is about variation or dispersion. Standard deviation From Wikipedia, the free encyclopedia In statistics, the standard ...
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calculate change in standard deviation when change in CI is available

For my meta-analysis, I would like to know how to calculate change in standard deviation when a change in mean and change in confidence interval (between baseline and endpoint) is available
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calculate the change in standard deviation for metaanalysis

I am trying to calculate the change in standard deviation for my metaanalysis. I have the following data available: mean for control group at baseline and endpoint mean for intervention group at ...
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Reducing bias for estimate of population standard deviation

https://en.wikipedia.org/wiki/Unbiased_estimation_of_standard_deviation#Other_distributions "For non-normal distributions an approximate (up to O(n−1) terms) formula for the unbiased estimator of ...
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Bootstrap sample estimate vs estimate of the sample

See wubers excellent answer in Mean of the bootstrap sample vs statistic of the sample Can somebody elaborate on the part regarding "BCa" and ABC. Let say you want to estimate the standard ...
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Large vs. Small Standard Deviation

I understand how to calculate the mean, variance and standard deviation of a given set of numbers, and I also understand the standard deviation is a measure of spread from the mean. In most texts (and ...
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How can I match two distribution to make them not statistically different?

apologies for the weirdly formulated question. I have two distributions, X1 (blue histograms) and Y1 (yellow). They are statistically different. I need to extract a subsample from Y1 (let's call it Y2)...
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Most appropriate calculation of mean and standard deviation for drug compliance?

I have 102 patients that were expected to receive 8601 doses of a drug in total. In reality, they received 7992 doses. I understand this to be an overall compliance of 92.9% in this group. Is this an ...
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Estimating error using a covariance matrix // The Economist US election model

probably a simple question. But I am working through the US election model that The Economist has open sourced - https://github.com/TheEconomist/us-potus-model/blob/master/scripts/model/final_2008.R ...
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How to estimate the standard deviation of mean squared error when both data and the fitting method are random?

Assume that in an experiment, $n$ training samples $(X_i,Y_i)$ are drawn i.i.d. from a distribution $\mathcal{D}$, $t$ test samples are drawn i.i.d from $\mathcal{D}$ too. Then a machine learning ...
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Finding the standard deviation with certain information

Is one able to get to a sample standard deviation with the following pieces of information? Mean, Median, Count, IQR We can assume it's a normal distribution.
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How could I designate a value, of which I could say that values above said value are greater than the others by a certain percent-data right skewed

Essentially I have 38 data points who have all been assigned a score that indicates how likely it is that this spatial point is going to be impacted by a natural disaster. I want to numerically ...
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Finding SD by only knowing the mean and one other piece of information

"The weights of bags of vegetables are approximately normally distributed with mean of 1kg. One quarter have weight greater than 1.1kg. Find the standard deviation." I know this question ...
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Percentage to Std-Deviation Calculator

This is such a useful function, and it should be possible if not analytically, then through a spline and lookup tables. How does one, in practical terms, go from percentage to standard deviations on a ...
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standard deviation of two constant noised signals related through interpolation

Let us say say we have a noised constant signal and want to evaluate the standard deviation (std) of the noise. We calculate the std of the said noised signal and call it σ1. Now we process the signal,...
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How can I determine the optimal binning system for a continuous variable in Python?

I've got two columns of data - a continuous variable that I'd like to treat as a categorical variable (i.e. bin it up), and a metric I want to measure by bin. Let's say the first column is income and ...
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Does standard deviation apply to any distribution?

What books have told me that 'standard deviation' has a special relationship with normal distribution i.e. 68–95–99.7% rule. What they didn't tell me is the answer to "can I use standard ...
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Intuition behind calculating a z-score

Given a sample, to calculate the z-score we do $$Z= \frac{X-\mu}{\sigma}$$ Intuitively, the standard deviation is an indicator of the spread of the data / the amount of variation, and the numerator is ...
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Is there a statistics method similar to Anova for groups of data that change over time (or other independent variable)?

My dependent variable (temperature), is time dependent (time groups 1-8, each 15 minutes apart). 5 different plants were measured. I want to know if there is a significant difference between the ...
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Lognormal model and standard deviation as a measure of variation

I am asking this since my math skills won't allow me to answer this question by myself. I have an outcome variable with the lognormal distribution. Thus, I use the lognormal regression parametrized as ...
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Chebyshev's inequality for Pareto distribution (3 sigma rule)

According to the Chebyshev's inequality, if we take any distribution, we get >88.8889% of data in +-3 sigma interval. For a normal distribution it is 99.97%. How to calculate the interval for a ...
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Which variation estimate to prefer: SD, geomSD, CV?

I have a case where we see regional disparities in median received services. Services is a lognormally distributed variable. Plot is based on a lognormal model, examining y and sigma. You can see that ...
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Gaussian error distribution: What does it mean to have a 5 sigma detection / confirmation of the expectation?

In experimental sciences you often hear of "5 sigma" detections/confirmations, where 5 is of course just an example. What does that mean? Suppose a theory predicts a certain quantity to have ...
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How do I find std.error with error propagation and for extrapolated data?

I have a table with different means. Some of the data is predicted future change, and the rest I have extrapolated. ...
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Standard deviation higher than min(X)?

Assume we have a roulette (single-zero wheel) and we want to figure the standard deviation for the first dozen numbers {1, 2, 3, ..., 12}. That gives us $\dfrac{12}{37}$ success probability and $\...
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Standard deviation and covariance of time series in slightly different time

Is it possible to stdev of multiple time series which have different length and different times? For example we have a data set, let's say a stock price or a family income ...
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Why is the standard deviation of the average of averages smaller than the standard deviation of the total?

Say I want to estimate the test error. I can either get $N$ batch $B_i$ then take the average of their average error (so the R.V. is the mean): $$ \frac{1}{N} \sum^N_{n=1} \mu(B)$$ or I can take ...
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How to check whether a partitioning is more balanced?

For example consider the following two partitions that add approximately to 100 percent. Partition 1 : 41% 36% 14% 5% 2% 1% <1% <1% Partition 2 : 82% 10% 4% 3% <1% <1% <1% <1% ...
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Estimating standard deviation of underlying distribution

I need to estimate the standard deviation of an underlying normal distribution. I have the following statistics of one sample: mean, min and max, standard deviation, and sample size; however, I do not ...
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Does Null Hypothesis affect Standard Error?

Here under $H_0:P_1=P_2$ the standard error gets some common $P$ value which is computed from a pooled estimate. Why is the $\sigma$ value not calculated in a similar way in the next one? There under ...
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Sample size calculation with different standard deviations

when calculating the required sample size with a given power and p threshold, usually the calculator only requires two estimated population mean and standard deviation. is it always valid to assume ...
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Distribution of sample sets drawn from a normal distribution

I'm not very well versed in statistics, but I have a data analysis project that tests a certain type of data fitting algorithm with simulated data. I want to validate my initialization logic of the ...

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