The expected value of a random variable; or a location measure for a sample.

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7 views

Is there a statistically significant difference between two methods, which test should I use & am I violating random assumption?

I collected data for every 2016 Republican primary that has available at least 3 polls, according to the polling data aggregated by RealClearPolitics.com. In a spreadsheet for each row which indicates ...
5
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4answers
269 views

Should I use an average to summarize ordinal data?

I need to work out a "average" (for lack of knowing a better word) of ratings or perhaps I could call them labels. Basically, I have a list of words that have been rated 1 - 3 for difficulty. 1 being ...
2
votes
1answer
19 views

How to get a mean from multiple categorical fields

I have some census data on income I would love to analyze. But income, in the data, is split into different income groups, each group is a column containing the number of people in an area that earns ...
2
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0answers
15 views

Higher variance in sample mean or sample median? [duplicate]

The variance of the sample median depends on the distribution you are sampling from. This is also true for the variance of the mean. But can one say that the variance of the sample mean is always ...
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3answers
12 views

What statistical method should I use to filter out the correct point?

My project is in the field of image processing. The output of a certain program would print the x and y coordinates in the image. I calculate the arithmetic mean of the points to get the mean ...
0
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0answers
13 views

Inference about two samples

I have two different large samples, one is normally distributed (0,1) and the other one follows a t-distribution (df = 4). Can I compare whether the means or the st. deviations of both samples are the ...
1
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0answers
14 views

Weibull, Gumbell and Extreme Value: from mean and variance to shape, scale and location parameter

I need to sample random numbers from Weibull, Gumbel and Generalized extreme value distributions. Of all of these distributions I know mean and variance. My question is: how can I determine these ...
0
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2answers
21 views

Co-Variance of Zero and Non-Zero mean random variables

Is the value of co-variance function for non-zero mean random variables different from the value of co-variance function when random variables have a zero-mean? I think yes based on this: For a ...
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0answers
10 views

Standardized difference of means

Standardized mean difference is very straightforward when you have 2 distributions / groups. How is this metric computed when you have >2 groups? Is there a better alternative to determining the ...
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0answers
28 views

How is knowing the mean of a set of data set useful? [closed]

Does someone know how is knowing the mean of a set of data set useful? And why?
0
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1answer
27 views

Calculating Standard Deviation of the Volume of a Cube

Let's say I have a machine that makes cubes. My goal is to determine the average and standard deviation the volume of a cube. I have N length, width and height measurements. I do not believe these ...
0
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0answers
12 views

What n to use for significance of correlations in three different scenarios

I feel these questions might already be answered around here somewhere, but I was not able to find it, so here goes. 1) General case of time-series When determining the significance of a correlation ...
0
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0answers
13 views

panel data mean and standard deviation

I have panel data of the form $r_{it}$ i.e. I have repeated observations of the random variable $r$ varying over individuals (i) and over time (t). Let's assume I compute the grand mean and sd of ...
1
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1answer
35 views

Robust statistic for representing small dataset with outliers and representing them graphically

I'm evaluating different systems varying a certain parameter common to all of them. Let this parameter be x. At each x value I ...
1
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1answer
20 views

Calculating speedup confidence interval

Summary I'm trying to calculate the confidence interval for speedup of a program when I have many measurements for the old and new execution times. Details Speedup is calculated as: ...
0
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0answers
14 views

Variance of subsample?

Total sample = subsample 1 + subsample 2 I have the mean and variance of total sample and subsample 1. I have n for total, subsample 1 and subsample 2. I can calculate the mean of subsample 2 ...
0
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0answers
9 views

Combine multiple means and upper/lower standard deviation values

I need to combine the means and upper/lower 1 sigma values for three different estimates of the same parameter. For example, a given set of means (m) and ...
2
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0answers
24 views

Comparison of two means when they are means of means?

I have two vectors "A" and "B". Each vector contains multiple mean values derived from observations. The two vectors are subsets of a sample that has been categorised into five vectors. All vectors ...
0
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0answers
16 views

mean\medians as data points in two way repeated measures ANOVA

I have a table with 12 columns each regarding one combination of three (2X2X3) diffrent conditions in an experiment. Each row (25) represent a subject that did the experiment. Each data point in the ...
0
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0answers
36 views

What is zero mean and unit variance in terms of image data?

I am new to deep learning. I am trying to understand some concepts. I know "mean" is an average value and "variance" is deviation from mean.I have read some research papers, all say that we ...
1
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1answer
47 views

Confidence intervals for group means (R)

Here are some sample data in R: set.seed(42) df <- data.frame(g = factor(rep(1:2, each= 50)), y = rnorm(100)+rep(0:1, each=50)) One can easily get group means ...
3
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1answer
47 views

Negative variance result when calculating standard deviation

Please note, I am still in secondary school so please keep your answers simple. A question on my homework states to calculate the standard deviation from a given frequency table with several class ...
-1
votes
1answer
35 views

Sample mean and sample variance [closed]

The sample mean is $\bar X = \frac{1}{n}\sum_{i=1}^n X_i$ and the sample variance is $S^2 = \frac{1}{n-1} \sum_{i=1}^n (X_i - \bar X)^2$ Can someone please explain how the sample mean and sample ...
0
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0answers
24 views

How to calculate Mean and Standard deviation in Lognormal distribution where only P90 and P10 are known

I have P90 and P10 of a lognormal distribution. P90=142.56 and P10=3415; I need to estimate the mean and standard deviation of this lognormal distribution. I have done the following steps and then ...
1
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2answers
169 views

The average of mean and standard deviation

I have the mean and standard deviation for body temperature ( in a group of people n=10 ), which measured using a thermometer in the left axilla, then in the right axilla ...
3
votes
1answer
56 views

How do I find the expected value of F(isher)-distribution

$E(F)=\int xf_{k,m}dx$ where $f_{k,m}(t) = \Gamma(t)=\frac{\Gamma((k+m)/2)}{\Gamma (k/2)\Gamma(m/2)}k^{k/2}m^{m/2}t^{k/2 - 1}(m+kt)^{-(k+m)/2}$. How do you find $E(F)$? Say you have to convert ...
3
votes
1answer
39 views

When confidence intervals of two parameters do not overlap with the mean of the other, why is it considered to be statistically significant?

Consider two parameters with means A and B with 95% confidence intervals. If the confidence intervals of the parameters do not overlap with the mean of the other, why is it considered to be ...
-1
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1answer
31 views

Learning Statistics [closed]

I am new to statistics and I am trying to get my head around 'why' some of these are calculated the way they are and what they mean, or were they just made a preference that stuck? - the statistics ...
1
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0answers
30 views

ANOVA : mean or variance?

I am confused about the ANOVA method in Statistics. ANOVA stands for analysis of variance. It is used to compare the mean between several groups. We use a test of variance (Fisher) for ANOVA. So, is ...
5
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2answers
293 views

What does it mean to say that “the population mean is a single fixed number?”

I am trying to figure out what it means if a population mean value is fixed.
0
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0answers
32 views

Good algorithm to compute the sample mean and variance [duplicate]

I am looking for good (fast, memory efficient, ideally one-pass) algorithms to compute the sample mean and variance. I have found a technical report by Chan, Golub, and LeVeque from 1983 with ...
0
votes
1answer
21 views

Test for significance of peaks (maximum) in time series

I have a time series of values, something like this: ...
1
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0answers
19 views

Cross correlation of gaussian signals with its mean signal gives non-gaussian distributed scores

The following is my question: I have signals that contains noise, they are of the following form see the figure below.. Then I take the mean signal of all these signals (identical in length and ...
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0answers
26 views

Probability of Non-exceedance modelled by Normal Distribution Question

The complete question is: A number of pre-cast beams are to be laid side-by-side to form a bridge deck which will later receive an in-situ topping. The beams are nominally 300mm wide, but in practice ...
0
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0answers
18 views

Outliers detection or some roubust metrics on long tail sqewed distributions

I have a distribution of user sessions on the web site in the following format date,sessionId,price 2010-01-01,1,0 2010-01-01,2,0 2010-01-01,3,10 ... And I am ...
0
votes
1answer
30 views

Measure of Central Tendancy in ARIMA?

I know very little about the ARIMA - the AutoRegressive Integrated Moving Average - model but I am interested in what type of central tendency is represented by "average". Is it simply the mean? If ...
1
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1answer
21 views

Measuring forecast accuracy of the conditional mean

Consider a dependent variable $y$, independent variables $x_1,\dotsc,x_K$, a model $$ y = X \beta + \varepsilon $$ and an estimated coefficient $\hat\beta$. If the model is assumed to be well ...
1
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1answer
27 views

Compare several means with different sample sizes (greater than 2)

I have seven different groups with different sample sizes and variances and I want to compare the means of their data. I'm not very informed in statistics, so could anyone help me out here? I've only ...
0
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0answers
25 views

Anova Profile Plot - Estimated Marginal Means understanding

I would like to ask you a question with regards to the Profile Plots generated by SPSS for 2x2 ANOVA (with balanced design). I have two Independent Variables, each one with 2 levels, and a Dependent ...
0
votes
1answer
22 views

Can one calculate a general mean for questions that use different scale length?

I have two sets of questions: 1). 5 questions with answer options from 0 to 10 (very unsatisfied to very satisfied) and 2). 9 questions with answer options from 1 to 6 (same meaning) The study was ...
0
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0answers
25 views

Real world example where mean is multiple orders greater than the standard deviation

This question is related to my research work. As it says in the title, I wanted to know if there exist any real world examples where the mean is multiple orders of magnitude larger than the standard ...
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0answers
12 views

Bird eye view of unknown data set [duplicate]

Pardon me if this question does not fit this site (or SE engine in general) but I do not know where to post it. Suppose that you have unknown data set which you want to explore. What ...
20
votes
9answers
3k views

Regression to the mean vs gambler's fallacy

On the one hand, I have the regression to the mean and on the other hand I have the gambler´s fallacy. I have had a good performance in the last game and, according to the regression to the mean, ...
0
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0answers
6 views

Detecting and Identifying Superpositioned Normal Distributions

I have data with populations centering around two means, one higher and one lower, as shown in this histogram. Is there a standard mathematical or algorithmic way for me to detect this occurrence ...
2
votes
3answers
917 views

If the mean and median underestimate the true central tendency, why use them?

In skewed distributions, both the mean and the median can easily underestimate or overestimate the true central tendency. For example, have a look at this violin plot: The median is shown here in ...
0
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0answers
22 views

Guarantee Period - standard deviation and mean given

I need some assistance regarding 1.2. Please can you advise whats the best solution? I seem to have worked out 1.1. The life span of an imported brand of kettles sold by an appliance giant is ...
2
votes
0answers
16 views

Bootstrapping A Mean: What is the significance (if any) of a converging mean for n iterations?

I have a stochastic signal, and I'm taking its mean in the canonical way and comparing that with a bootstrapped mean: ...
0
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1answer
10 views

Size of Mean Squared Error (MSE)

Is there a rule or a scale for judging if a certain MSE is small, very small, big or very big? Please give also a source to underpin your recommendation.
0
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0answers
39 views

Is this sample drawn from the normal distribution ? using information from both mean and standard deviation

After correcting for a bug in my code in a previous question, I could simulate efficiently thousands of samples from the normal distribution N(0,1). I calculated the mean and standard deviation of ...
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0answers
36 views

Is the sample mean a better point estimate of the population median than the sample median?

A beginner's question to check I've understood correctly. A basic stats textbook says: "The variance of the sampling distribution of the median is greater than that of the sampling distribution of ...