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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Standard deviation of a coin flip bet
What is the standard deviation for the pay-offs of a coin flipping game where you get 2 dollars if heads and lose 1 dollar if tails. How does the standard deviation change if the probabilities remain ...
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42 views
Can you divide a standard deviation?
I have 4 domain scores (means), but for the population they are multiplied by four in many studies (don't ask why), but my means are not. So I divided the means by four, but can I do the same for the ...
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45 views
High standard deviation: rule of thumb
I know this is a pretty vague question but I was wondering if there was a rule of thumb relation between the mean and the standard deviation of a given set of values by which you can say "Something's ...
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57 views
Estimating the population variance [duplicate]
I'm trying to understand the emphasized phrase in the following passage:
The usual method of determining the probability that the mean of the population lies within a given distance of the mean of ...
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84 views
Retrieving standard deviations from OLS estimates
I am running a fixed effects regression in Stata: $y=\alpha+\beta D$ (omitting the FE), where $D$ is a dummy variable. Basically, I want the mean of group $D=0$ and of group $D=1$ after controlling ...
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25 views
normally distributed [closed]
It can be assumed that residential lot sizes in Baycoast are normally distributed with a mean of 1150 square metres and standard deviation of 350 square metres.
Any residential lot size in Baycoast ...
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43 views
Measuring Similarity of two Transient Signals
I am trying to measure the similarity between two signals, i.e. how identical they are.
A complete overlap (two lines forming a single line) should give me a value of 1, the greater the distance, ...
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58 views
Standard Deviation of Binned Observations
I have a dataset of sample observations, stored as counts within range bins. e.g.:
min/max count
40/44 1
45/49 2
50/54 3
55/59 4
70/74 1
Now, ...
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23 views
Marketing research survey results
I added a question about marketing research survey result. There are two questions and two results related to this survey. Can you help me answer these questions about this data sheet.
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20 views
Variance of superset from variance of subsets [duplicate]
Let's say I want to estimate $var(A)$ of a list of numbers $a_i \in A, i\in [0,N]$.
However, I only have the variance of the non-overlapping, and complete ($B \cup C = A)$ subsets $B$ and $C$.
...
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45 views
Non-linear regression, plot mean, SE in R
I need to create a graph like the one below.The idea is that I have three data groups with 5 replications on the first two groups and 3 replications on the last one. I must obtain a regression curve ...
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35 views
what does this +/- of “average” mean?
I have a set of data points and I was told that for it to be valid, every data point should be within +/- say 5% of the average of the entire dataset.
I have no problem of checking each data point ...
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68 views
Finding Abnormally Low Ticket Prices
I'm creating a program where my goal is to analyse lists of ticket prices and locate tickets that are priced abnormally low in relation to the spread of prices.
My preliminary model does the ...
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2answers
76 views
Why Normalization (Standardization) values should be smaller than $1$?
The books gives some examples about content based recommendation. An example of what I understood is at below.
A movie's attributes are values between $1$ and $10$. The duration attribute gets ...
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35 views
How to create the class range given 1 as the middle class, 3 as the highest value and 0.65 as the lowest value?
Good day. I know getting the class interval given 3 as the highest value and 0.65 as the lowest value is easy. Here's the catch, the distribution of the interval starts at 1 which is considered as the ...
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71 views
Determine sample size without knowing standard deviation
I want to calculate the required sample size for a call centre with a finite population.
The survey will collect data on many variables. The objective is to gain data about a range of psychological ...
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1answer
38 views
How to standardise cases within groups to perform ranking across groups and over time?
I am trying to create a method to rank ships according to their fuel burn rates. There are two different classes of ships, with different burn rates, so I am trying to create a mean and standard ...
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45 views
How to decide whether the distribution is unimodal or bimodal in grain size distribution?
In the examples given at this link, I am not able to decide whether the distribution is unimodal or bimodal. I think it is in between unimodal and bimodal, but I do not know if this kind of class ...
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2answers
97 views
How to compute weighted means and SDs?
I want to calculate volume weighted average price and standard deviation for the following dataset:
...
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32 views
How can I convert annual standard deviation to a longer period?
Quicken provides annual standard deviation of returns for a given portfolio using analysis done by the Newport Group. I'd like to convert this to a longer term number--say 10, 20, or 30 years.
...
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75 views
Why do we refer to our estimates in terms of precision?
Open any statistics textbook and it will urge the need to check the 'precision of our estimates'.
Take the following random variable:
...
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1answer
52 views
Test for comparing “mean of means”
I have a treatment and a control group. Both groups consist of several teams, each with several individuals. When I want to compare the performance between the groups, I could run a t-test or Wilcoxon ...
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28 views
Comparing the magnitude of the standard deviation with the average value
For calculating the concentration of an unknown sample, my average value after three trials was about .03425 +- twice the standard deviation (.00159)
In comparing twice the standard deviation to the ...
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300 views
Is it possible to find the combined standard deviation?
Suppose I have 2 sets:
Set A: number of items $n= 10$, $\mu = 2.4$ , $\sigma = 0.8$
Set B: number of items $n= 5$, $\mu = 2$, $\sigma = 1.2$
I can find the combined mean ($\mu$) easily, but how am ...
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2answers
68 views
Gamma function, unbiased estimation of standard deviation
According to the Wikipedia article, the following estimator of the standard deviation
$$s=\sqrt{\frac{1}{n-1}\sum_{k=1}^n(x_i-\bar{x})^2}$$
for a normal variable, verifies $E[s]=C_4(n) \sigma$, where
...
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1answer
80 views
Interpretation of mean in this example
I recently presented a national test and the company in charge of preparing the test then does a standardization to provide the final scores for each person. These are the values they gave at the end ...
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57 views
Volatility model combined with different distributions?
I am working on fitting distributions to financial data using different volatility models. The simplest case of a gaussian distribution I do understand:
The data is $\mathcal{N}$$(\mu,\sigma^2)$ ...
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79 views
Standard deviation of revenue where numbers are only positive
Is there a way for standard deviation to ignore negative numbers? In other words, how can you make it so that 2 or 3 deviations do not extend into negative territory?
When looking at a set of only ...
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86 views
can I compare standard deviation and mean?
I hope no question is too simple. I am just learning, and I came across an expression that compared standard deviation and mean of a distribution. I thought that it makes no sense to compare them, ...
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103 views
Ordinal data, different scales, comparison between variables
I would appreciate any help you could give me
I have ordinal data which I want to standardise in order to compare averages and data spread between variables. I need to standardise since the variables ...
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2answers
227 views
Mean comparison for statistical significance
I was told to come here by a friend to ask a stats question.
I took Social Stats and Methods of Social Research about 4 years ago and to be honest, I don't remember much about it. Now I'm writing a ...
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2answers
192 views
How to quantify the effect of an independent variable on the standard deviation of the dependent variable?
My independent variable changes the variation in the dependent variable. The mean doesn't matter, just the variance. Bartlett and Levene's tests indicate a small p-value and thus significant ...
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1answer
23 views
Discrepancy between calculated and simulated error propagation
Just curious if anyone knows why there is a tiny but definite difference between the standard deviation as calculated by the error propagation formula and the simulation. It is only a 0.2% difference ...
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102 views
Bootstrap USL/LSL for non-normal data
This is new statistics space for me, so please excuse my ignorance.
I have some data (N=180) that isn't normally distributed (verified in Minitab, P<0.005) and I want to use the data to get a +/- ...
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100 views
How can I find the standard deviation in categorical distribution
How can I find the standard deviation in categorical distribution, where the elements have non-numerical attributes (e.g. colors)?
For example, I have a bag of marbles with $n$ colors. There's an ...
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112 views
Population Variance and Sample Variance
How is it that lowering the number of frequence,$n$ by $1$ in the for formula for Population and Sample Variance account for the discrepency of using sample rather than population.
I mean how is ...
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1answer
97 views
standard error of known population values
i tried to get a clearer understanding of the standard error by constructing a hypothetical population consisting of the following values: 1, 3, 5, 7. i calculated the sample means of all samples with ...
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Prove one assumption in confidence interval for difference in means
How to prove that
$\sqrt{( s_1^2 / n_1 + s_2^2 / n_2)}$ converge in probability to $\sqrt{( \sigma_1^2 / n_1 + \sigma_2^2 / n_2)}$?
$s^2$ converge in probability to $\sigma^2$, when n goes to ...
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336 views
How to get Standard Deviation from Mean Squared Error
So I've been working on the same question in my homework for days. I've done it over and over and I know I'm doing something wrong. I can't get a straight answer from anybody about it. I just want to ...
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114 views
Plotting means and standard deviations
Does it make sense to look at a scatterplot of means versus standard deviations in terms of looking for outliers or changepoints? So the mean is on the x-axis and the standard deviation is on the ...
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105 views
How is the distance formula related to the formula for standard deviation
The formula for the standard deviation of n numbers is the same as the formula for the distance between two points in n dimensions. Could someone explain why this is and how these are related?
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51 views
Use median for clustering, instead of average value
I have a List of Files on which I run some statistical methods to get a rating between 0 and 1.
Now i need to cluster the files for similarities. The easiest way i thought that would be is to use the ...
2
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1answer
122 views
Standard deviation of a particular dimension in a multivariate Gaussian distribution
I have a set (cluster) of vectors in dimension d. From this I have calculated the sample mean and covariance matrix ( I make the assumption that they are from a multivariate Gaussian).
My question ...
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2answers
120 views
Interpretation of an equation
I'm trying to describe the equation in the attached screenshot in my own words.
$\lvert(\overline\chi_1-\overline\chi_2)\rvert > s_1(t_{1 @ 99 \%}) + s_2(t_{2 @ 75 \%})$
The equation tests ...
3
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1answer
100 views
How to Calculate a Z-Score from Power Log Distributions
Please forgive me if the question is non-sensical as I only have a elementary knowledge of statistics, and I have no idea where to start.
I want to perform an analysis of some web analytics ...
2
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1answer
94 views
Normal distribution in R
I am trying to check what is the probability that a new observation is anomalous or not?
Suppose I have the following set of observations:
...
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38 views
Calculate standard deviation of data within each bar of a histogram [duplicate]
I have data with which I plot a histogram.
I would like to know the standard deviation of each bar of histogram.
Do you think it is an acceptable method to divide the samples into sub-samples for ...
2
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1answer
1k views
Standard deviation of a ratio (percentage change)
I have 2 data sets. The first data set, let's call it $X$ has an average value of ($\bar X$) and standard deviation of ($STD_X$), the second set of data also has the average value of ($\bar Y$) and ...
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Computing weighted standard deviation using lowess mean values
I have two questions:
First question:
I want to compute the weighted standard deviation with tri-cubic kernel. I am using lowess function in R to compute the weighted mean using tri-cubic ...
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Measuring dispersion of tokens within a text file
I am working on a code analyzer application. It is essentially a piece of software that parses and interprets other programs' code and comes up with various metrics, findings, statistics, and ...
