# 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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### Staggered Average and Standard Deviation of incomplete dataset

I have an AxBxC matrix of measurements, from which an arbitrarily-sized-and-distributed number of measurements have been deemed invalid and removed (i.e. that matrix contains a mostly random ...
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### How can I calculate the R-squared of a simple linear regression only with sample size, the coefficients and its standards deviations?

I have the following estimated simple linear regression, which was estimated from a sample of 1217 individuals: $\hat{y}=1.77663 + 0.0910103x$ where $\hat{\beta_0} = 1.77663$ and standard deviation of ...
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### Weighted Average

I'm trying to calculate essentially, how fast I complete certain tasks irrespective of the mix of tasks that I'm assigned. In other words: In Year 1: Client Average Task Time Number of Tasks Client ...
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### Is it reasonable to calculate a T-test or Cohen's d with one group's sample size, mean and standard deviation being averaged or pooled?

This is my data: year 1: n, mean, sd year 2: n, mean, sd year 3: n, mean, sd year 4: n, mean, sd year 5: no data year 6: n, mean, sd (special event happened) Sample sizes, means and standard ...
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### Statistical conclusions from incompatible measurement results

I assume that the following situation is not uncommon in scientific practice: Two research groups analyse two samples. The reported results concern the same physical quantity at the same location ...
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### How do i estimate how many items in a sample are outside 1 standard deviation of the mean?

My question is how to estimate how many samples are above 1 standard deviation of the mean. I do not know individual values, hence why it's an estimate. The sum of x is 243 sum of x^2 is 2317, n = 30, ...
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### How to estimate mean confidence intervals for a sample of a population with the population standard deviation?

First off, this is my first question on stats exchange. So if I mess up or anything, please let me know because I know this website is a lifesaver, and I want to spend more time on it. Recently, I ...
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### What statistics describe a distribution uniquely and completely? [closed]

I have a very weird and possibly amateurish question. I have a situation where I need to keep track of some activity until some event occurs. I want to store that activity (say, a series of 0s and 1s),...
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### Find consistency measure for a seller selling a product every week

I a working on a use case where I need to find the consistency of a seller for selling a product every week. Consider there is a product X which is being sold by multiple sellers (seller A, seller B, ...
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### Obtaining standardized mean differences or pooled standard deviation for linear contrasts

I have a weighted linear regression with three categorical predictor variables (each with 4 levels), and have tested three contrasts using the multcomp package in R: ...
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### Determining the standard deviation based on standard deviations from 2 data sets (paired)

I would like to run an analysis on the effectiveness of a drug on a specific parameter. In 1 study, mean and SD values were reported at baseline, and post-treatment for both experimental and control ...
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### Statistics terms in French

I am reading through some statistical PhDs in French and the term "ecart-type" is used, which my dictionary gives as standard deviation, but from the mathematical context I think that in ...
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### Why does NSL report Std. Err that is equivalent to the NIST reported SD

I am running a verification using the NISTnls package (https://cran.r-project.org/web/packages/NISTnls/NISTnls.pdf). When I used the example code for the supplied functions, e.g. Chwirut1: result <-...
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### Can someone help me to find a study/dataset of height differnces of men and women including normal distributions and their standard deviation/s? [closed]

i am currently interested in a study or a valid data set of height differences of men and women. What I am explicitly looking for is something with normal distributions and their standard deviation/s. ...
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### What is the difference between Type A and Type B uncertainty evaluation?

I am trying to evaluate the uncertainty in measurement following the Guide to the expression of uncertainty in measurement (GUM) elaborated by the Joint Committee for Guides in Metrology. Link: https:/...
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### What does 0.5sigma mean?

I want to ask about a term about "this data is within 0.5 sigma". If I understand correctly the person first calculates standart deviation(sigma) of his data and multiples his/her std ...
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### Efficiently find the group with largest effect on standard deviation

I have some "groups" of measurements with varying numbers of items, for example: ...
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### Can I use a Modified Z-score with skewed and non-normal data?

As per z-score it assumes data comes from normal distribution, Modified z-score can work with data that is skewed. My question is it good to use modified z-score for a data that is not normal?
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### How to estimate minimum sample size to achieve a certain confidence interval?

The title of this question is a bit general. Allow me to elaborate. Context I'm measuring a biological parameter (BP) of different subjects. For each subject, BP follows a normal distribution, with ...
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### How to compute standard deviation in case of transformed scores?

I have a set of data made by 2 variables (V1 and V2). For each variable, the values are between 1 and 7. Now, to calculate the summary score according to the guidelines I must apply the following ...
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### measure for deviation/error that is guarantueed to be smaller than the mean

I am presenting some non-negative values by using a mean value with error bars, basically something like this: So the mean values are shown as dots and the error bars are displayed vertically, ...
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### Why is the correlation coefficient always smaller than $1$ and bigger than $-1$?

I kind of see that the covariance is similar to the product of the standard deviations but I can't figure out how. My problem is that I don't understand how does this formula tells us how strong the ...
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### Can you calculate pooled standard deviation from just the sample standard deviation?

For a meta analysis, we are calculating cohen's d from data reported on published articles. For a specific article, only standard error (SE) and mean difference (between treatment and condition) are ...
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### Calculating the confidence interval for the mean value from a sample

The central limit theorem states that the means of many different samples with n>30 from a population that follows an arbitrary distribution are normally distributed. If you now have the ...
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### Westfall says, "the proportion of the kurtosis that is determined by the central $\mu\pm\sigma$ range is usually quite small" but is the reverse true?

In his article that debunks the notion of kurtosis as measuring distribution peakedness, Peter Westfall writes, "[T]he proportion of the kurtosis that is determined by the central $\mu\pm\sigma$ ...
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### How to calculate aggregate standard deviation for composite scores in a meta-analysis

I wonder if someone would be kind and able to provide guidance/suggestions on a stats issue that myself and colleagues are trying to handle while performing a systematic review and meta-analysis. In ...
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### Error (SD) on means of multiple binned datasets?

I manipulate a few datasets and wondering what would be appropriate when calculating the error (standard deviation mostly) Lets say I have 3 datasets (A,B,C) with ranges 1:1000. These datasets are ...
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### Bayesian update (considering normal distributions as model) always decreases the standard deviation

I am trying to refine a sensor measurement using Bayes rule to update the sensor value $x$ after consecutive measurements. I model the sensor value with a normal distribution $P(x) = N(x; \mu, \sigma)$...
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### Calculating the variance of a function which depends on the standard deviation and mean of a random variable

I am a bit new to statistics and had some conceptual questions regarding the calculation of variance. I want to calculate the variance of a function $y=\frac{\sigma_{X}}{g(\overline{X})}$. As seen in ...
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### Standard error of the mean and fits

I am trying to understand what kind of statistics I should use to correctly report a mean value. Essentially, I have a number of curves that belong to the same population, and I use the same model to ...
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### Understanding my standard deviation output

I'm trying to run some variance/standard error calcs for NPS (net promoter score) which is calculated as (# of promoters - # of detractors)/total surveys How can I calculate margin of error in a NPS (...
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### How to calculate the variance and standard deviation of a collection of percentages? [closed]

A firm you are analyzing has had the following returns the past 5 years: 27.0%, 33.0%, -40.0%, -14.0% and 22.0 %. What are the standard deviation and variance of the past five year returns? I have ...
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### Is there a way to quantify the amount of spread of a plot of mean values over time?

I have a plot that is a mean of multiple measures of a motion over time with error bars 1 standard deviation away on the positive and negative side, which are calculated for each time point. I am ...
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