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Questions tagged [standard-deviation]

In Probability and Statistics, the standard deviation of a statistical population or data set is a measure of how much variation or dispersion exists from its average value. It is defined as the square root of the variance. Use this tag alongside (statistics).

In Probability and Statistics, the standard deviation of a statistical population or data set is a measure of how much variation or dispersion exists from its average value. It is defined as the square root of the variance.

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Standard deviation of flipping coins

My question deals with flipping a coin. I figured out that in one session of flipping a coin 400 times, the standard deviation for a 95% confidence interval is 20. I understand this to mean that (95% of the time) tails could come up 220 times and…
user271108
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Why do RMS and Standard Deviations sum squares?

I've seen some references to this - or a few examples of it, but for some reason it's not clicking. Can anyone give me a good layman's explanation of why calculations such as RMS values and Standard Deviations insist upon squaring all the values…
Brad
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Understanding standard deviation

If the mean is 50 and the standard deviation is 10. I am told that this means that "most of my data" falls within 10 points of 50. So "most of my data" is between 40 and 60. But what does this "most of my data" mean exactly? Does it mean 51% of my…
avkaapstad
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Uncertainty of measurement with goniometer

I got a goniometer with scale -90 to 90 degree. I use only 0 to 90 degree. One section of the scale has 1 degree. I read a value of $62^\circ$. What is the uncertainty of this measurement? I thougt like this. If one section has $1^\circ$, then I…
user50222
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combined standard deviation

I am new to Standard Deviation. I have taken a 2 small samples of Data and obtained the mean, and Standard Deviation. I have copied and pasted a picture of my spreadsheet. As you can see i have worked out the SD and mean of each group. I have…
Mr Assistance
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How to calculate standard deviation from mean and probability?

What's the formula to calculate the standard deviation knowing the mean and a certain probability, but not knowing all the n's. http://stattrek.com/online-calculator/normal.aspx For example, ^that calculator only requires mean and a probability of…
John
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Standard Deviation: Can I remove some data?

Suppose That I have measured property "X" in 16 points of a rigid body. This rigid body is consisted of two different materials. In one of them, property X is around 1, and in the other X is around 5. When I measured X, I found a transition zone of…
sasan
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Solving Probability using standard Deviation and Mean

Given a normal random variable with mean 90 and a standard deviation 3, find the probability that x is greater than or equal to 86.67 and less than or equal to 96.33
Alex
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Standard deviation of binned sample

I have to calculate the rms size of some sample (let's say 1D for this case). When I only have limited resolution my rms value gets bigger. What's the name of this effect again? Is there a way to correct for it? Could I reduce the error by using…
magu_
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How do I get the sample deviation from population deviation when sampling is done without replacement from a finite population

How do I get the sample deviation from population deviation when sampling is done without replacement from a finite population? The deriving step by step was needed. enter image description here
Dunken Zhao
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Is there a relationship between the harmonic mean and the arithmetic standard deviation?

I was doing a thought experiment on the harmonic mean. Let's say we have a sequence of 4 numbers: 100, 110, 90, 100 The arithmetic mean (AM) of this sequence is 100 but the harmonic mean (HM) is 99.4975. Let's imagine that the initial and final…
Feynstein 100
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Can I use std dev on a data set of 'diminishing returns'

Sorry, I don't know the math words. I have a data set that looks like the following. I am counting things, and the graph shows how many of each thing there is. for example, I have a LOT of thing #0, and not many of thing #300. In my application,…
Tony Ennis
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Compare standard deviation with out using the standard formula

I very well know that Standard Deviation is the measure of spread of the data. If the data has higher deviation from its means then it has higher standard deviation. What if the data has same mean and range and just a couple of values changed…
Animesh Pandey
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Trying to understand the standard deviation's formula

I have just started learning standard deviation and I'm trying to understand the formula. $$ s = \sqrt{ \frac{\sum(x-\bar x)^2}{n-1} } $$ Can anyone explain to me the square (and square root) part? If they are using the square & square root to…
Just a guy
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Converting mean and std deviation of degrees from Fahrenheit to Celsius

Given the conversion table of these data points of temperatures in Celsius and the respective value in Fahrenheit: \begin{array}{|c|c|c|c|} \hline C & 10 & 20 & 30 \\ \hline F & 50 & 68 & 86 \\ \hline \end{array} To calculate the mean in…
jackw11111
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