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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 ...
321 views

### How to calculate a new mean from different means for my Systematic Review and how to calculate a new SD?

I am currently doing a systematic review on distal radius fractures. I want to give a mean age and sd in my systematic review. Therefor I need to calculate the mean from all the different means of the ...
402 views

### Threshold value for Cluster after document similarity

I have N documents. I have found out cosine similarity between all documents. T = (N*(N-1)/2) Because docSim between a document with itself is 1. Now, I have one query and I want to find out all ...