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.

learn more… | top users | synonyms (2)

0
votes
0answers
6 views

Error bars from a set of points at different x values [on hold]

Say I have a set of 4 data points all at different x values. They fall approximately on a line, with fairly small noise. How can I estimate the standard deviation, or some reasonable measurement of ...
0
votes
0answers
23 views

Errors-in-variables multivariate polynomial regression (R)

(EDIT: the question has been modified just a little bit to be more specific) I want to fit a multivariate polynomial regression that accounts for measurement errors (an Error-in-Variables model). ...
3
votes
1answer
65 views

“normalizing” std dev?

First of all, I'm not a statistics person but came across this site and figured I'd ask a potentially dumb question: I'm looking at some P&L data where the line items are things such as Sales, ...
1
vote
0answers
8 views

x and y standard deviation estimates in linear regression power analysis

I want to run a power analysis on linear regression against the null that the slope is equal to zero. Specifically I am trying to estimate what sample size I will need to obtain a specific power level ...
3
votes
1answer
29 views

R - lm how to get standard deviation coefficients

I have a very simple problem but I cannot find the answer anywhere. I run a linear model with lm() and I want the standard deviation coefficients in order to compute the confidence interval. I know ...
1
vote
0answers
15 views

Relation between bootstrap mean and parameter value estimated via maximum likelihood

I have an observed data set $O$ and a synthetic model $S(\theta)$ which attempts to describe it. By fixing $\theta$ to different values I can generate $M$ synthetic realizations of the model: $$S_k ...
0
votes
1answer
16 views

Normalising extreme items within datasets

I have a a dataset where each item is a % above or below 100% (taking an individual item, dividing by the mean). In order to produce a rank I weighted each item by a % (summing to 100%) to provide a ...
0
votes
0answers
19 views

Statistical Significance Without Normal Distribution nor Equality of standard deviation

I have two datasets consisted of 4 columns. I have to measure if the differences among the data (each column represent another data) are statistically significant. The problem is that: in the first ...
4
votes
2answers
99 views

Best statistics to show outliers beyond 2 SD

I try to perform scheduling for an organization based on client flows. We are very seasonal. Our senior management in Washington, DC make us base our schedule on the mean number of clients we have ...
4
votes
1answer
69 views

What is the standard error of the sample standard deviation?

I read from there that the standard error of the sample variance is $$SE_{s^2} = \sqrt{\frac{2 \sigma^4}{N-1}}$$ What is the standard error of the sample standard deviation? I'd be tempted to guess ...
1
vote
0answers
21 views

Should I use a composite standard deviation for these multiple biological/technical replicates?

I used an ELISA to determine protein concentration from absorbance readings, which is a nonlinear relationship. I have 3 sample types, which are broken down into 3 biological replicates (per sample), ...
1
vote
0answers
23 views

Alerting framework for incoming traffic using mean or standard deviation

Currently I put hourly traffic (total number of input requests) of my website in a MySQL table. I keep data for the last 90 days. I want to check every hour, lets say 6th hour, that whether the ...
1
vote
0answers
16 views

Using Standard Deviation to Understand Consensus

I was recently asked a question, and while I think I know the answer intuitively, I can't explain it. Scenario: A questionnaire of 20 questions was given to 6 people. Each person was asked to ...
0
votes
0answers
29 views

Can we use normal distribution statistics on frequency distribution outputted by bootstrapping?

If I understand correctly, this is the bootstrapping procedure: Pretend sample is population Repeatedly resample from this pretend-population Calculate the mean of each resample. The output of ...
0
votes
0answers
18 views

Standard error of a ratio of differences of estimates

I am interested in calculating the standard error of a ratio of differences of estimates, like so: $SE(\frac{X_2-X_1}{Y_2-Y_1})$ The s.e. of each difference is easy, ...
3
votes
0answers
8 views

Geometric Mean Standard Error [duplicate]

I read from wikipedia that the geometric standard deviation is $$\sigma_g = \text{exp}\left( \sqrt{\frac{\sum_{i=1}^n\left(\frac{A_i}{\mu_g}\right)^2}{n}}\right)\,, $$ where $\mu_g$ is the geometric ...
4
votes
2answers
95 views

use standard deviation as predictor?

My question is simple: is it statistically valid to use the standard deviation of a group of data points (X) as a predictor for Y? I am dealing with data that looks like this: Well, at some point ...
1
vote
1answer
36 views

Standard deviation of a casino's profit

For the following question, I've determined the mean to be \$0.20, but how do I determine the standard deviation? A slot machine at a casino pays out an average of \$0.9, with a standard ...
0
votes
0answers
20 views

How many experiments for measuring of standard deviation

I want to get standard deviation of variable. How many data I need to to obtain correct value? What is correct approach to estimate amount of data I need? What precision I need to say it is precise ...
0
votes
0answers
30 views

Binning by standard deviations

Quick question: I came across a fairly respected source on running Markov Chain Monte Carlo for bayesian statistics in ...
0
votes
2answers
62 views

When using SVMs, why do I need to scale the features?

According to the documentation of the StandardScaler object in scikit-learn: For instance many elements used in the objective function of a learning algorithm (such as the RBF kernel of Support ...
0
votes
0answers
15 views

How would I average noisy data representing the noise using error bars?

I have data that was binned in a process that provides the average and standard deviation for the values in each bin. For some of the data, the variation between bins is significantly larger than the ...
0
votes
1answer
21 views

Standard Error for Weighted Values

I want to calculate the standard error for an experimental measurement. The data is stored as a 2D image which is circularly symmetric about a center point. To reduce the data we radially integrate ...
1
vote
0answers
20 views

Can you calculate descriptive statistics (SD, SE particularly) from percentages and ratios?

I'm a cell biologist and a lot of my data is expressed as a fraction (percentage) of the total number of cells in a single experiment in a number of separate categories (generally 5 or so). The number ...
1
vote
0answers
37 views

How can we get “estimated standard deviation” from MLE?

I'm looking for MLE as in the following picture. I have some questions: How can we get "the estimated standard deviation"? Is "the estimated standard deviation" included in the output of the ...
1
vote
0answers
29 views

How can we calculate the standard deviation of multiple values with different uncertainties each?

For example, if I have a set of readings, like: 13.4 +/- 0.5 14.5 +/- 0.7 12.8 +/- 0.6 13.9 +/- 0.4 14.8 +/- 0.5 How do I calculate the standard deviation of ...
1
vote
0answers
22 views

Standard deviation comparison for splitting clusters in ISODATA

I am currently implementing the ISODATA algorithm and I am new to cluster analysis as I just learnt about it. I got stuck at the step which I need to compute the standard deviation of each cluster, ...
0
votes
1answer
37 views

Is my Interpretation of this statistical distribution correct? [closed]

The torque of shld flx action was between 8Nm to 10NM for 10% of the time Is my interpretation correct? If so how do I determine torque for one of the 19 activities?
0
votes
0answers
26 views

calculating error for percent inhibition

I'll apologize in advance for leaving out pertinent information as I'm sure that I will. It has been a long time since I've devoted any time to statistics, so bear with me. I have 2 sample sets, a ...
0
votes
0answers
58 views

threshold based on mean and standard deviation

I have a time series of 70000 data points. I want to separate samples of this time series which have very large values as compared to the time series. How can i threshold sample to separate. What i ...
0
votes
1answer
93 views

Confidence intervals vs. standard deviation

The 95% confidence interval gives you a range. The 2 sigma of a standard deviation also gives you a range of ~95%. Can someone shed some light on how they are different?
0
votes
0answers
64 views

Bounding the bias of standard deviation estimate for stratified sampling (MC)

I cannot find an answer to this issue: in Monte Carlo runs, if one uses stratified sampling then the unknown bias of the variance estimator ( $\bar{\sigma}^2=\frac{1}{N}\sum{(y_i-\bar\mu_y)}$ where ...
0
votes
1answer
30 views

Comparing mean differences between groups when standard deviation in one of them is 0

I was wondering if it is possible and -if yes- what are the implications when one is trying to compare mean group differences of a continuous variable that varies in one group but is a constant number ...
0
votes
0answers
44 views

Median Absolute Deviation vs Standard Deviation

To measure spread we use Variance or Standard Deviation. Variance and hence Standard deviation uses mean to find out the spread. Recently came across the MAD (median absolute deviation). ...
0
votes
0answers
56 views

How to plot mean plus/minus standard deviation for histograms?

I have a set of grayscale images, where the pixels may have values in the range $[0, 255]$. From each image, I calculate a histogram, which shows how many pixels have the value $0$, $1$, $2$, and so ...
0
votes
1answer
22 views

Measuring share contribution of each var/cov term to the standard deviation of a sum of variables

Say, for a simple example, I have a random variable $X = \alpha_1 X_1 + \alpha_2 X_2$, where $X_i$ are random variables and $\alpha_i$ are weights. I then calculate the standard deviation of $X$ as ...
2
votes
1answer
32 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 ...
1
vote
1answer
29 views

Multivariate Standard Deviation

I'm not sure I'm describing this 100% correct, but here goes. Is there a way to find out the overall standard deviation of a data point if it has multiple variables? For example, If I have the ...
1
vote
0answers
58 views

How to calculate mean and standard deviation of a range variable (grades) when the raw data is based on frequency categories?

Results of an exam indicate that: 13% of the class earned an A 20% earned a B 48% earned a C 10% earned a D 9% earned F's The grade C ranges from 70-79%. Assuming that the data is normally ...
2
votes
1answer
79 views

How many samples needed to determine value 4 sigma away from mean?

I have a source that generates computer files varying between 20,000 and 40,000 bytes in length. I think (strongly assume so) that they vary in length according to a Normal distribution. They average ...
0
votes
1answer
56 views

Making the most of Standard Deviation and P value — graphing?

I have a question or two in regard to getting the most out of the statistics of my data. By way of background, my qualitative observations of two distinct populations that are uniformly regarded to be ...
0
votes
1answer
30 views

Random Walk Probability Including Drift

What is the equation for the probability of a random walk with drift being equal to a specific value after n steps, given a specific standard deviation?
0
votes
2answers
18 views

Determining parameters for distribution of standard deviations

I have a database of 10-star movie ratings (similar to IMDB), with a large number of movies and an also large number of ratings for each movie. For each movie I have computed the mean and stddev of ...
0
votes
0answers
41 views

Standard deviation error bars and kruskal.test in R

I need to test if there is a significant difference between two groups of data, each with three replicates. (Multiple groups) I used the following approach: ...
0
votes
1answer
37 views

Distribution of the stddev of movie ratings

I have a database of 10-star movie ratings (similar to IMDB). For each movie the raw data is a distribution of votes from 0-star all the way to 10-star, and I have also computed the mean and standard ...
3
votes
1answer
52 views

Is it correct to use plus or minus symbol before standard deviation?

I have represented standard deviation as "±SD" before in publications. But I like to have opinions on this. Is it appropriate to use the notation '±' with SD ? Or is it only for Standard error ?
1
vote
0answers
38 views

Why is standard-deviation considered to be L2 distance?

I'm trying to really understand what SD is telling me, but the information out there is sparse and confusing. This thread and some others as well provide the answer that SD is L2 distance in ...
0
votes
0answers
18 views

NMSE - division by zero

I am using the normalized mean square error function in the Python Oger Toolbox which is defined as: ...
0
votes
0answers
29 views

Averaging standard deviations of unequal weight?

I'm sorry if the title is unclear, but I'm not sure of the appropriate way to phrase this question. I'm in med school (and sadly not as versed in statistics as I ought to be), and I am trying to use ...
0
votes
0answers
24 views

how to estimate scale variance only using item sd's and scale reliability

The problem I encounter is that I need to estimate the scale variance of a psychometric scale without having the original data. The only information I have is the means of the (binary) items, their ...