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Questions tagged [standard-deviation]

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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How to calculate the error of percentages

Is it correct to calculate the standard deviation of four percentages/proportions as you would for four numbers (i.e. non-percentages)? As an example, the aim of my experiment was to measure how much ...
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Standard error of the population from a bootstrapped distribution

I would like to compute the Std. Error (SE) of some statistic (lets call it a). Given than the distribution of a is usually not normal, I performed a bootstrap. I am not sure how to compute the SE ...
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Why do we round up the Standard Deviation when it rounds regularly to 0? [on hold]

Why do we round up the Standard Deviation when it rounds regularly to 0? For instance, if our SD is 0.02, we round it up to 0.1, but if it is 0.06, we keep it at 0.06. Can someone please explain? ...
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Does 1 divided by standard deviation tell us anything? [duplicate]

(1/standard deviation) I've seen someone use this and I would like to ask for clarity on this because the intuition of it isn't immediately obvious. Standard deviation tells us how dispersed the ...
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Standard deviation in multimodal data

I have a dataset, 90% of observations are unimodal normal (with couple of outliers per feature), 10% are mixture of normals, components have the same standard deviations. Data contains outliers => ...
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Statistical test for replicate measurements with mean and standard deviation

I am having some trouble trying to find the right statistical test for my experiment. It is a flow cytometry experiment with many replicates and I am comparing normal and disease states. I get a ...
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Summary statistics [closed]

Code I have used the output it is generating So I am trying to use calculate the summary statistics ( SE, SD, CI) of my data which consists of 5 fly mutants grown on 2 different treatment options. ...
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Get better confidence interval by drawing multiple samples

Imagine that I have population of size N and I draw a sample of size n from which I compute a proportion $\hat{p}$ of a categorical variable. And I want to get a confidence interval of 95%. So I ...
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Does this mean my model is useless?

Long story short, I have a random forest I've created. It's mean absolute error is .209 for the test set. The (scaled) standard deviation of the y column is .201 (for all the y column data, not just ...
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1answer
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different formula to calculate standard deviation

I have a naive question. I have list a a = [1, 2, 3, 6] . mymean = sum(a)/len(a) To ...
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1answer
46 views

“Average” standard errors of multiple samples

let's assume that I have 3 subjects with each of them producing 5 values. Now, I can calculate the mean, variance, standard deviation, and standard error for each subject. Each subject has its own ...
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Estimating sample size en poussant

If we have sample mean of $n$ observations as $\bar{x}$. It is given that maximum value of the whole set is $M$ and minimum value is $0$. How many more observations we need so that the estimate for ...
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How can I determine standard deviation in excel given the probability that values will fall within a defined range?

Assuming a normal distribution with a mean of zero, if I am told that 68.2% of the population values are within +/- 4.7, I can conclude that the standard deviation is also 4.7. But what if I am told ...
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Does standard error for a sample mean make assumptions about the distribution?

Suppose I calculate standard deviation of a sample mean as $ \sigma / \sqrt{n} $ where $\sigma$ is the population standard deviation and $n$ the sample size. Have I just made an assumption that the ...
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Can I directly obtain standard deviation using an Excel formula knowing only median error rate, but no sample size? [closed]

I have access to statistical data with a median error rate of 4.7%. This means half of values fall within an error rate of 4.7%, and half fall outside this range. The sample size is not provided, but ...
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What Mean Should One use for CUSUM change detection?

I'm new to CUSUM and I'm using it to detect change of temperature over time past a certain threshold. My data are daily temperatures from July through October, and I am using 0.5*SD for my C and 5*SD ...
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Standard deviation in a non normal distribution

I have two datasets, dataset A with 5-10 values and dataset B with around 20 values. Both are non normally distributed and right skewed. Can I use standard deviation to compare the elements ...
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How to compare 2 regression models?

Suppose I have 2 regerssion models A and B, and dataset for evaluation containing N samples, ...
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Can I derive category thresholds/intervals when the categories are defined as a set of means with standard deviations?

Imagine you have a set of scores between 0 and 100 ("SUS Scores"). Based on the distribution of hundreds of these scores people have tried to provide adjective "grades" for these scores such as "ok", "...
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Relationship between standard deviations of partitioned subsets and the standard deviation of the whole set? [duplicate]

Let's say we know the standard deviation of a set of data. Furthermore, that set of data can be partitioned into subsets, and we know the standard deviation for each subset of that partition. What's ...
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How to find the variance and SD using the raw score formula? And what is raw score formula

I read in the book of Statistics in Plain English by Thimothy Urdan (DOI: 10.4324/9780203851173) that you can find the standard deviation and variance using the raw ...
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2answers
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How is the standard deviation in this coin tossing experiment calculated?

I'm reading Hypothesis Testing: The Basics, there is such an experiment: So, we have a coin. Our null hypothesis is that this coin is fair. We flip it 100 times and it comes up heads 51 times. Do ...
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Standard deviation of sum of samples from Bernoulli/Binomial

This should be simple I hope. In lecture notes from a physics course, the professor writes: $\text{Prob(success)}=\dfrac{k}{N}$. So query $q$ times, see some number $\mathcal{l}$ successes and ...
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2answers
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Repeated measurements descriptive statistics for whole period

I am looking at the number of doctor’s visits over a 10-year period in about 2000 municipalities. Each municipality is assigned to one of five municipality types (e.g. large town, rural community, ..)....
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how to combine standard deviations and mean for each group?

I have a table with 10000 rows, each row having 10 columns and their numbers vary from 0 to 80.Now, if I want to compare the mean of these rows.Maybe because of the largeness of one of the numbers in ...
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1answer
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Is it normal for principle components to have the same SD?

I'm trying to determine outliers of a PCA by calculating the sd of the eigenvectors - however it returns the sd as equal for each PC. 1) Is this normal and 2) Is this the right approach for ...
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Roughness of time series or physical measurements

I am facing regularly the same issue regarding the stability of my physical measurements. How stable is my equipment? How noisy is my signal? For example, I apply a current on a resistor and want to ...
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Simulating noise around future known data points

I am creating a simulation model of an electricity market. One of the important characteristics is fuel price. Whilst I would like to set the future fuel price, I would like to sample from a ...
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1answer
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Find data points that deviate the most in 2D graph

I have a set of data points where X axis represents the percentage of disk space, and Y axis represents the memory used by an application. In general, higher the disk space, the higher memory it'll ...
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Understanding STD, SEM and CI

Trying to understand the difference between std and sem: ...
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4answers
137 views

Standard error or standard deviation?

I'm trying to self learn some topics in Statistics by reading Statistics by David Freedman. There is something that I cannot understand regarding the standard error. I have been reading in Google ...
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2answers
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Combining two means and SDs of one group [duplicate]

I have the mean & SD of several different time points, I want to combine them into one mean and SD. Is it possible? Example; At 1 hour; mean=5, SD=1, n=42 At 2 hours; mean=6, SD=3, n=42 and so ...
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1answer
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Subtracting two means and convert to %. What happens to the standard deviation

I have two sets of data to track the changes of my subject of analysis. I collected at two different time points, time = 0 and time = 10 min At time = 0 min, the raw data are [12, 9, 10]. mean is 10....
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SPSS: Comparing prevalences

I have a dataset of couples presenting themselves to the infertility clinic and would like to compare the prevalence of certain diseases in this group to the prevalence of these diseases in the ...
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1answer
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Statistic to Verify Subsample is Similar to Original Sample?

I have a subsample of data (120 students) that was taken from an original sample of 1,216 students' data. I need to report in my manuscript whether my subsample's key demographics (age, gender ...
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What do my mean and standard deviation tell me?

I have American State level unemployment rates in 3 waves of longitudinal data. When I describe unemployment rates for my descriptive table I get the following: ...
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How to derive SD from difference in means in paired data?

I am doing a meta analysis, so I am collecting data from manuscripts. I need to obtain the mean and standard deviation for timepoint 1 and timepoint 2 for a variable called mpg but the paper only ...
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1answer
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The Standard Error in R language lm (linear regression) is Standard Deviation or Standard Error of the Mean?

When we are estimating the coefficient in R, "Std Err" will be produced by "lm". Is it Std or SEM? How is it calculated? Run lm function with any R data set will give an example.
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How to get standard deviation when the only given information is sample mean and p-value

I have a question for an exam: You read a journal article on TOTAL-cholesterol, HDL-cholesterol and LDL-cholesterol from a study of n=100 patients where TOTAL-cholesterol = HDL + LDL cholesterol. ...
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1answer
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How to calculate the standard average of a set excluding outliers? [closed]

I have a set of numbers, and I need to calculate their average excluding outlier values (which I don't know a priori). It came to mind that many years ago I studied Standard Deviation. Could I apply ...
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1answer
53 views

Log transformation to generate random number producing NA's

I am trying to generate a random values using log distribution. The reason for using log-distribution is keep the values positive. ...
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1answer
42 views

Can mean,standard deviation of different populations be similar?

Sorry for the dumb question. Perhaps this is too obvious but i don't see it. Will appreciate any help. We're analyzing a gene expression dataset of 64 autistic individuals vs 82 normally developed ...
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1answer
42 views

How can I understand my standard deviation?

I have some (2749) sensor output values. They range from 0 to 1769. With google spreadsheet I put it thru some calculations to get the (mean) average and standard deviation. With this I created two ...
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1answer
29 views

Calculate Standard Deviation of hour

I have standard deviation for each 15 min of that hour so can i calculate the standard deviation of that hour using this 4 standard deviation values ? Reason Standard deviation of each 15 min is ...
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1answer
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If we change only one value of a data set, will the mean absolute deviation behave in the same way as standard deviation?

I took the new data as b and the data removed as a and calculated the new mean and used that to find the new mean and deviation in terms of the old. But it gets too complicated and there is no way to ...
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Meta-analysis in metafor package with within-subjects standard error?

I am conducting a meta-analysis with metafor in R. For the majority of articles, I managed to extract means and standard deviations, which I need for the escalc function to calculate an effect size. ...
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1answer
57 views

How to calculate divergence from standard deviation

I have 20 people I wish to give performance score every 6 months. I want to identify the weakest performers in the bottom 10 and remove them from the group but only those from the point of the most ...
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Standardize gpx data (GPS Points) to calculate overall distance and duration

I'm using Strave (www.strave.com) quite a lot for my sport activites (3-5 running/cycling activites per week). Strava offers to download all your activites in raw data; means you could download all ...
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How to compute the probability a non-deterministic crash being fixed

A problem I encountered a few times and I always had problem answering my boss's question:"Are you sure it is fixed?" I would really like to be able to give an answer along the lines : "Before the ...
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How to quantify the uncertainty in a single value obtained from a large number of simulations

Im a physics student working on a project in which I have to simulate a machine that would order a bunch of molecules according to their mass. I want to get a quantitative measure of how well the ...