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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Showing deviation of data on a fixed scale

I'm creating a chart in D3 which shows the Mode from a large (1mil +) dataset; and colors it according to the standard deviation of the dataset. But the issue is that I need to map the range (Red ...
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Standard deviation of travel times

Suppose that travel times for Swinburne students are normally distributed with mean of $32.5$ minutes and a standard deviation of $5$ minutes. Complete the following sentence, giving figures correct ...
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201 views

Measure dispersion of a set of values resides in a range

I want to know what is best method to calculate (measure) the statistical dispersion of a set of values resides between a range. Scenario: My goal is to build an index. I have two methods that ...
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253 views

GRE - Standard Deviation

The frequency distributions shown above represent two groups of data. Each of the data values is a multiple of 10. Quantity A = The standard deviation of distribution A Quantity B = The standard ...
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Gaussian of different standard deviation and sample spacing

For given a set of samples position (e.g. $-2,-1,0,1,2$) I can define the correspondent, normalized, gaussian weights for a gaussian with std. deviation $1.0$. I know that if I scale all the sample ...
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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 ...
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196 views

Average and Standard Deviation for Angular Values

I'm trying to characterize an inexpensive accelerometer that provides (roll, pitch, yaw) values by generating basic running statistics (mean and standard deviation). But I'm unfamiliar with ...
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46 views

Variance reduction factor using gaussian filtering

I am currently trying to find the variance reduction ratio using gaussian filtering. For a simpler filter (as mean filtering for example), I am able to calculate it easily to find the well known ...
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47 views

Normal Distribution,standard deviation and probability question.

According a study, the duration of a match in World Cup is approximate normally distributed with the mean 111 minutes and standard deviation 5 minutes (including the break between the halves). ...
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Does “Expected Absolute Deviation” or “Expected Absolute Deviation Range” exist in stats and have another name?

So everyone is familiar with Variance and Standard Deviation from high school, but it seems no one has any familiarity with a philosophical justification for such weird, seemingly arbitrary measures. ...
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finding the variance of a complex scenario

construct a sequence of cubes with one vertex at the origin and having lengths 1/2^x, x=1,2,3,... Select a point randomly from the unit cube with one vertex at the origin and sides of length 1. Let ...
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47 views

Determine standard deviation of nonlinear model parameter?

I have some experimental data to which I fit $h+e^{-\gamma t}(a\sin\omega t - \phi)$. The result looks like this: My ultimate goal is to find $h$ values. Now, I could find something similar to $h$ ...
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44 views

Summing standard deviations? or summing variances?

I have a method for making measurements. Within this method there are four separate variables that can influence the measurement (i.e. variation). I have individually tested each variable (by making ...
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How to derive a Gaussian mean's functional dependence on a variable

I have three variables: $E, I,$ and $X$. $I$ is a function of $E$: $I(E)=gauss(\mu(X), \sigma=1)$ I sampled this distribution with a very simple $\mu(x): 3\times x$. I want to fit that data to ...
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330 views

How to add standard deviation regarding MATLAB function normrnd(mu,sigma)?

My question depend on this scenario which is as follows, I used a MATLAB function "normrnd(mu,sigma)" with mean 'mu = 0' and S.D 'sigma = 5', to generate a normal random number "R1". I added this ...
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103 views

How to calculate Standard deviation with mean 0 and Min and max value on x-axis is -1 and 1 respectively?

How to calculate Standard deviation with mean 0 and Min and max value on x-axis is -1 and 1 respectively? It is of-course a normalize distribution. I apologize in advance for stupid question.
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Adding stochastic variables random variables where one has time component

Based on GLS regression I have identified two random variables lets call them A & B ...
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Population confidence interval from sample SD and sample mean?

A sample has: $$\text{a sample size } n = 70,$$ $$\text{sample standard deviation } s = 184.43,$$ $$\text{and a sample mean } \bar{x} = 564.15.$$ Compute a 95% confidence interval for the population ...
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Is the variation of the mean 0, and the variance of standard deviation just the variance?

Just trying to get some properties straight. Was looking at a problem online which reads: Let X be a random variable with mean μ and variance σ2. What is the variance of X/σ+10μ? The solution of ...
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Monte Carlo standard deviation of the mean estimate too small.

I'm doing a Monte Carlo calculation and use the standard deviation of the mean $\sigma_M$ as the error. To get an estimate of this from the regular standard deviation I use $$\sigma_M=\dfrac\sigma ...
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Confused on Expected Value

I have this question in which I have solved so many times but unsure of the answer i have. could anyone help out? ** A cpu manufacturer has a machine which produces microchips. The probability ...
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Variance test: how to tell which is sample 1 and sample 2?

I'm using this variance test to see if I have unequal variance in my data: I am not told which is sample 1 and sample 2 in the questions, just the alternative hypothesis. So is there anyway I can ...
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27 views

Clarification on z-score

I have been reading a Statistics book and they show the following formula for z-score: $ z = \frac{x - \mu}{\sigma}$ And then they explain about the $\mu$ and the $\sigma$ in the formula like this: ...
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Find StdDev of a percentage list

I need to find Standard Deviation of a percentage list, e.g. [0.5, 0.8, 0.8] in Python would give: ...
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SD from Mean and Median

Given the mean and median of a dataset, is it possible to compute the standard deviation of the dataset?
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Value of n to ensure the mean is within a 95% confidence interval

A random sample of size n is obtained from normal distribution. Calculate how large n must be to ensure that the sample mean lies within 0.25s.d of the mean with probability of 95%. I know the ...
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Bioststistics review

The Mean serum-creatinine level measured in 12 patients 24 hours after they received a newly proposed antibiotic was 1.2mg/dl. If the mean and standard deviation of serum creatinine in the ...
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84 views

Standard deviation with multiple means and deviations

The amounts of a certain mineral that can be produced in a day from mines $1$, $2$, and $3$ are independent normal random variables with means equal to $80$, $90$, and $75$ pounds, respectively, ...
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Exponential deviation with two $x$ values

I recently got interested in this topic of standard deviation. My TA did not have any time to go over this topic so I was trying to teach myself it recently. My TA said if he had more time he would ...
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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 ...
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129 views

Margin of error for quotient of two measurements

I need to find the total margin of error for calculating velocity, while I have margins of error for time and distance. Actually the margins are the same (as both measurements were based on GPS - but ...
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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 ...
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30 views

Standard deviation shouldn't reduce?

I need to do a algorithm to calculate an integral via Monte Carlo Method, and for a purpose of simulation, I need to calculate the standard deviation of a sample generated in my program. My problem is ...
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Uncertainty on an estimator

Well first I want to say that I have a very weak background in stats/probability but I still hope that the question I want to share with you makes sense. I have a set of binary (coming from a set of ...
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Can I calculate the new standard deviation when adding a value without knowing the original set of values?

I have these three mathematical values that describe an unknown set of values. Mean (population mean, not from sample) $\bar{x} = 3$ Standard deviation $s = 1.5$ Number of elements in population ...
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probability, normal distribution mean [closed]

Should I use a certain table for this question or should I use a special formula. A random value has a normal distribution with the mean 102.9 and the standard deviation 4.7. What are the ...
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I need help with this review question. Business Calculus/Statistics

The question is: The scores on a test have a mean of 100 and a standard deviation of 8. A personnel manager wishes to select the top 60% of applicants. Find the cutoff score. Assume the variable is ...
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Variences and adding them from independent random variables?

If I have 3 random varibles X, Y and Z and X=Y+Z then var(X)=var(Y)+var(Z), but Y=X-Z therefore var(Y)=var(X)+var(Z), it is clear that these two contridict, so what makes one of them right and the ...
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How do you calculate deviation from optimal value?

The variables I have: The optimal Tour Cost My Tour cost - I executed this 30 times, so I can get the average? Standard deviation just tells you how spread out the values are, I dont think thats the ...
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How to weight three different variables to create a ranking

I have data on the graduation rate, tuition, and average student income (a measure of accessibility) for about 7,000 colleges and universities in the U.S., and I'm trying to compose an interactive in ...
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51 views

Estimate standard deviation of sample

You have a random sample of 25 objects with mean weight of 24 grams, estimate the standard deviation of the sample. In addition, you know it's supposed to be 25 grams with a deviation of 1 gram, but ...
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323 views

Conclusions to be drawn from mean, median, stdev, and range

From a sample of size n = 100, the following descriptive measures were calculated: median=23, mean=20, standard deviation=5, range=35; 75 sample values are between 10 and 30; and 99 sample values are ...
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Taking the standard deviation over multiple assignments?

Lets say that a group of students all take 5 tests, with the average and standard deviations as follows: test 1: mean 43/50, SD 8 test 2: mean 23/30, SD 4 test 3: mean 56/70, SD 12 test 4: mean ...
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40 views

Probability and Standard Deviation

Hey I'm confused about how to do this kind of problem. I can't figure out how to find the standard deviation. There are on average 4 tetanus cases reported in the US each month. What is the ...
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how to find standard deviation when given a percentage?

I'm stuck on this question, can anyone help? An electronics company's biggest seller is a talking toy. Of the toys produced, 4% have a defective voicebox. A quality control tech randomly collects 250 ...
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“Reverse” distribution-tails

Chernoff, Markov and Chebyhev all give some upper bound for tail probabilities, e.g. Chebyshev gives us $Pr[|X-E[X]| \geq t] \leq \frac{Var[X]}{t^2}$. This is quite helpful, but what if I would ...
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Mean and variance: Gaussian is the most conservative assumption

"given only the mean and variance of a distribution, the most conservative assumption that can be made about the distribution is that it is a Gaussian having the given mean and variance" I've read ...
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stdev and mean from gaussian fit vs. from classical formula

I have a set of data - measured speed of molecules in water. I made a histogram and fitted it with function $$A\exp\frac{(x-B)^2}{C}$$ calculating mean and standard deviation from values B and C If I ...
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Problem on Standard Deviation

A man has observed the number of chocolates eaten by his son for 32 days.The total number of chocolates eaten by his son is 80 and the sum of the squares of the chocolates eaten everyday is 1000, then ...
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Confidence intervals and dividing by $n^{0.5}$

I am studying a-level and am confused when I divide the standard deviation by $n^{0.5}$ when doing confidence intervals. To put it another way when I don't divide by it? (where $n$ is the number of ...