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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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Calculating standard deviation from log-normal distribution confidence intervals

I have the results of a meta-analysis of 10 studies that reports a combined random effects odds ratio (computed using Woolf's method) and 95% confidence interval of an event happening in one group ...
520 views

Evening out a set of buckets

(I am not strong in statistics so please forgive me if I don't use the correct terms here) Let's say I have a book with many (1000+) sections, and each section varies significantly in the number of ...
2k views

Why do we need the SD line?

Why we need the SD line(magenta) and how does it help us, besides just passing through all standard units of x and ...
959 views

Which normalization method for different units (zero, negative, etc.)

Commonly, normalization of ratings seems to mean adjusting values measured on different scales to a notionally common scale. I have different metrics that measure different performance aspects of a ...
291 views

Derivation of prediction intervals for a normally distributed population with unknown population standard deviation

I have via the ISO standard 16269 found the solution to a problem that I've been working on. Based on a couple of independent samples from a normally distributed population, I would like to determine ...
2k views

Propagation of uncertainty/standard deviations in biological experiments

I am trying to work out how to propagate standard deviations in a biological experiment, but I have some difficulties. I have the following (semi)fictitious data originating from an image analysis ...
74 views

Why is the population standard deviation approximated as the sample standard deviation?

This question addresses calculating a p value from the mean and standard deviation statistics of a sample. I understand that the -general- philosophy is to divide the sample standard deviation by the ...
319 views

Analytical linear regression vs cost function

I'm trying to fit data to a line $y=ax+b$ (you can download it in this gist). You can see a fit in the next image: To do so, I'm using analytical methods of minimization of the cost function, defined ...
51 views

Why is the standard deviation the error on the singular measurement?

I'm a beginner with the study in data analysis in Physics. I'm trying to understand the meaning, in the field of experimental Physics, of the standard deviation $\sigma$ of a series of data. There ...
2k views

Detecting outliers in non-normal distribution data

I'm working with data from a resistivity test. However, during the test it is common that a few measurement points are wrong due to technical failure. So I want to find and remove these points. I ...
78 views

Distribution of ratio of 2 points drawn from normal distribution?

Let's say we have a known normal distribution $N(\mu,\sigma^2)$. I now draw 2 points $p1$ and $p2$ randomly from this Gaussian distribution for every observation, and repeat this process large number ...
212 views

Backing out the standard deviation from information on baseline mean/s.d., and coefficient mean/s.d

I am trying to run a power calculation for a randomized control trial. For this I need a mean and standard deviation for our 'baseline'. There are papers out there which would have a mean and standard ...
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 ...
194 views

Set of data and averaging/standard deviation

I have a set of data (positive real numbers < 1) in five categories. My aim is to show that the data in the last category is bigger than the other categories for a range of examples (the data set), ...
24 views

Statistical dispersion metric for single extreme value

I have around a million sets of 8 datapoints. I would like to rank these sets of 8 data points. I am trying to identify sets where there is a single extreme value and the other 7 datapoints are of ...
57 views

How to read the mean and standard deviation from a Q-Q plot

I wrote the following code in R to make the following qqplot. In a question I am asked to read the mean and standard deviation of the sample off the plot. I see ...
30 views

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 ...
82 views

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What are the most adequate parameters for assessing bias in propensity scoring systems?

I am analyzing a very large dataset featuring scores in a sport. The only information I have is the scores of many athletes in various locations, which are organized in the following way: ...
76 views

Simple descriptive statistics with inter-quartile mean. What about standard deviation?

If one summarizes a data set with an inter-quartile (iqm) mean, rather than the mean calculated using the complete data set, is a standard deviation (sd) calculated using the complete data set then ...
106 views

modelling the standard deviation as a function of x?

This may be very simple. Consider the following figure, minus the robot. How can I model the standard deviation of Speed as a function of Rep I can chop the rep up into arbitrary pieces (e.g. 2000 ...