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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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Chebyshev's theorem

OK, so here's the question (not my homework - which is line segments -_-) According to Chebyshev's theorem, how many standard deviations from the mean would make up the central 60% of scores for this class? [What are the corresponding…
Mateen Ulhaq
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Calculate standard deviation from ratio of two variables

Ok here is my problem. For my research I am investigating if we can use twitter to create sports data. One part of the problem is for example this: We now for example that in the 6th minute of the game a goal is scored. Now we need to know by what…
Javaaaa
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Standard error of the estimate

Question: In order to estimate the total weight of rice of 100 bags, a sample of 25 bags was weighted, giving the average weight of 50 kg. If the population standard deviation is 1.5 kg, estimate the total weight of 100 bags and find the standard…
user3575652
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Add value to known mean and Standard deviation

I have a distribution that will continuously have numbers added to it as they are measured. I want to keep only knowledge of the mean, the standard deviation, and the number of values so far in the distribution. How would I go about adding a new…
3Pi
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Combining standard deviations

We have two groups measuring the same resistors, the nominal value is unknown. Group 1 is slower and because of that they did not calcute the s1 empirical standard deviation. Group 1: N1=500 , R1=6900 , s1=unknown Group 2: N2=20 , R2=6880 ,…
Tony
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Alternative Standard Deviation Calculations

I recently inherited some code that does bounds checking from a coworker no longer with the company. It has the following comment //Currently, we use 3 sigma(standard deviation) as upper bound, where // sigma = SQRT(mean * (1 - mean) /…
Kobaj
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Standard deviation used in confidence interval for mean

I am a novice to Confidence intervals. To figure out the confidence interval for mean, one could either use the $Z$ distribution or t distribution depending on the sample size and population standard deviation. When the size is less than $30$ and…
Raji
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Is it possible to calculate standard deviation if I have sum of squares and number of samples as input?

I have following inputs Sum of the squares of the numbers. For example if the numbers are $1,4,6$ the sum of squares is $53 = 1^2+4^2+6^2$. And I have the number of input samples: $3$ in this case. Is it possible to calculate the standard…
Akshat Jiwan Sharma
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Normalising Standard Deviation as score for Burstiness calculation

I have measured the frequency of terms within the same period (say 14 days), and I wish to use Standard Deviation to calculate their burstiness (i.e. which terms are more spiky), therefore, if a term is constantly high count but due to their low…
drhanlau
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Clarification: Expression to calculate the standard deviation when data is scaled to interval [0,1]?

For an experiment, the standard deviation (SD) is entered as a parameter for generating gaussian noise. The SD value is mentioned to be 25 when data (a matrix) has integer values in [0,255]. If the data was scaled to be within [0,1], what would be…
VanguardExplorer
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finding percentiles with standard deviation

This is a question on my worksheet that I'm not sure how to start: If you know that the mean salary for your profession is $\$45000$ with a standard deviation of $\$2000$, to what percentile does your salary of $\$41240$ correspond?
Raven
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In calculating the standard deviation, why do we square the difference from the mean, as opposed to cubing?

This question has been bothering me for a while: In calculating the standard deviation, why do we square the difference from the mean, as opposed to cubing the differences (and then taking the cube root at the end)? Is this just a random choice,…
JMS
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Find the variance of $x$ when the standard deviation is given in the form of $ax+b$.

The standard deviation of $3x+7$ is $4$; then what is the variance of $x$? I know that variance is the square of the standard deviation but how does $3x+7$ and $x$ relate?
swapedoc
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can STD of subsets be used to arrive at the STD of the whole set

Assuming I have a set of values called S and the STD of S is Xs. Let's say I split S into two subsets S1 and S2 with standard deviations X1 and X2. The number of elements in S1 and S2 are called W1 and W2. So my question is, assuming I have the…
Jose Martinez
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How can I figure out a set of values that most of my population will hit 99% of the time?

I am not a math person, I'm trying to put together a spreadsheet in excel that takes the square footage for every property in a county as the only input. I want to then generate a list of square footage range amounts that in plain english…
MVCylon
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