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

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12 views

Evaluating mean-squared error

Hello I am running a Regression Tree experiment. I am new to Regression Trees, and I am using Mean Squared error to test my tree. I am confused because I am getting a large Mean Squared Error but I ...
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1answer
26 views

How to calculate the variance for mean of means?

I have been reading up on how to calculate variance for different situations and the following has me confused….. If I take a number of samples (e.g. choose 5 kids in a class and ask them how many ...
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0answers
13 views

How can I calculate a confidence interval for true mean of one set being higher than another, based on samples from each?

I have two sets A and B each containing N elements and want to show that the true mean of A is less than that of B with certain degree of confidence. (Specifically, the sets represents items of "yes" ...
2
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1answer
50 views

What is $\bar\mu_n$?

Am I right in thinking that it is the average of the sum of $n$ different populations means? Here it is used in the context that confused me. It's the Chebychev WLLN, apparently. "If $x_i, i = 1, ...
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2answers
56 views

Comparing the mean difference between data measured by different equipment, t-test suitable?

My problem is as follows: I have 2 measuring devices, both using different measuring techniques, each trying to quantify properties of objects passing their measurement area. The devices measure the ...
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0answers
10 views

calculate mean for groups [migrated]

I'm doing a research about SATs scores by cities. I have every city coded. Is there any way to ask stata to calculate the mean for each city without having to type the city-code? Not having to write: ...
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0answers
23 views

Formula for “adjusted mean” - Is this correct?

I am working on a software project involving statistical analysis of myoelectrical signals (EMG). One client requested the calculation of "adjusted average" for a given signal interval. His ...
2
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1answer
28 views

Comparison of two means

Which test should I use, if I want to compare the mean of the whole sample with the mean of the fraction of the sample? So for example the mean of the whole classroom taking the test and the mean of ...
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1answer
29 views

Does the standard error assume the mean is the centre of the distribution?

In statistics we can calculate a mean of a sample and the standard error of the mean. Let's say the mean of a sample is 2 and the standard error 1.5. If we repeatedly sampled from this population, it ...
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0answers
23 views

Different means with barchart and descriptives in SPSS

I have a dataset (in SPSS 22) with different measurements of children, with the children in rows and with the measurements as variables in the columns. For example, the activity levels of the children ...
2
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0answers
29 views

Averaging z scores when doing a “group by”

I have a dataset where each row is an hourly measurement of certain fields (columns). For each column I then add another column that is its respective z score relative to the entire population. If I ...
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0answers
6 views

Problem with calculating the avarage power of a vector? [migrated]

I am calculating the average power of a vector. I would like to compare it the final expression with the simulation. However, they are not equal. Please help me to point out which steps are wrong. ...
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2answers
179 views

Drawing numbered balls from an urn

PROBLEM There is an urn with a set of balls where each ball is labeled with a different integer. The numbers on the balls are known and are not a range of integers. For example the set of balls could ...
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1answer
22 views

Using more measurements of lower quality or just the one with the best quality?

I am currently trying to analyze some pupillometry data. The device I use gives me X and Y measurements of the pupil area (from which I compute the total area via $A = \pi \times ...
3
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0answers
101 views

Better estimator of expected sum than mean

I am trying to find the optimal estimator for the maximal expected $\Sigma X_i$ where $X_i$ is sampled from an unknown distribution which is chosen to be maximal. To clarify and simplify, there are ...
0
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0answers
7 views

Comparing the means of correlations based on different size of sub-correlations

I would like to compare the mean correlation of two different sample groups: I had two groups of teachers who were judging their students' performance. One group of real teachers (N=10) judged on ...
2
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0answers
28 views

Largest eigenvalue of this random 2x2 matrix

Consider four random complex vectors $\mu_i$ of length $K$ whose entries are drawn from the complex normal distribution $\mathcal{CN}(\mathbf{0},\mathbb{1})$ centered in zero and of unit variance. ...
3
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2answers
107 views

How to calculate Estimated Arithmetic Mean for a lognormal distribution

I have been tasked to program functions from some Excel sheet into a asp.net app so it can be shared to my colleagues via a web interface. However, I am stuck on one thing. I have a set of variables ...
0
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0answers
25 views

Estimation of Noise Level in the High-Throughput Cancer Data

Assume that I have made a coverage log ratios signal by dividing the coverage data coming from a tumour sample over the reference sample and then taking the log2 of this division. My question is: ...
2
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1answer
45 views

Timeseries: Find points deviating from the mean

I haven't done much time-series modelling at all and now I have a dataset which screams "time series" at me and now I am hunting for a model. The data: Imagine a video watched by ~400 people, 100 ...
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1answer
56 views

$E(X_1| \overline X ) = \overline X$, the sample mean

Let $X_1, X_2, ..., X_n$ be a random iid sample from a population with mean $\theta$. Now I am wondering about the intuition behind $E(X_1| \overline X ) = \overline X$, the sample mean. If we just ...
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0answers
30 views

How to calculate mean on group statistics

How can I calculate the mean of the first schema? I don't have the individual values of the sample. Std. Deviation (B) is 0.6441.
2
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1answer
65 views

Why do means&error bars in an ANOVA graph depend on the factors and covariates that define it?

I have a mixed-model design with between-subjects factors Group (treatment, control) and Difficulty (easy, hard), and within-subjects factor Timepoint (pre, post). I want to use my statistical package ...
3
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1answer
144 views

Question about standard deviation and central limit theorem

I have a quick question about the central limit theorem. Lets say I measure some value that comes from an arbitrary distribution N times and I repeat this M times. I understand that if I calculcate ...
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1answer
35 views

Estimating a distribution based on three percentiles and a mean

I have a set of percentiles the 10-th, 50-th and 90-th. Furthermore I have the mean value. I am trying to reconstruct the underlying distribution. The question is similar to Estimating a ...
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0answers
19 views

Symmetry of a distribution

I have received a sample, summarized by a frequency table with groups (i.e. 1-7, 7-10, 10-13, 13-16, etc...) I calculated the mean and median, both were around 15, the mean was 15.3, the median 15.6. ...
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28 views

Adding mean and standard deviation to each other

I make a certain measurement and I would like to arrive at a single descriptive number that would give me an idea of both the average value of the measurement, as well as the deviation from the mean. ...
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2answers
29 views

Shouldn't a weighted t-test and a weighted linear regression yield the same standard error on the estimated mean?

I have a vector of values and a vector of the reciprocal of their standard error. I'd like to estimate their mean and the standard error on the mean. At first I used linear regression using the ...
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0answers
18 views

Testing equality of mean vectors

Which is the best method to test equality of mean vectors say that of age, height, weight and BMI of 150 men and women?
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26 views

Is one-way ANOVA appropriate for comparing differences in (calendar) monthly means?

I have data for solute export by month (monthly mean values with year aggregated so that n=12), in one-way ANOVA the groups should be independent. A month of high solute export will probably lead to ...
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0answers
31 views

Probability that a sample mean is between two values using Central Limit Theorem

Mean is $2.707$, standard deviation is $.049$, sample of $35$ is drawn from the population. What is the probability that the mean price for the sample was between $2.683$ and $2.716$? It was suggested ...
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1answer
39 views

Variance of sample mean for dependent samples

Suppose I have two discrete independant random variables $X$ and $Y$, and that I'm interested in the expected value of the random variable $W$, where: $$ W= \text{sign}(X-Y). $$ So, W is 1 if ...
2
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1answer
55 views

Standard error of mean

I am learning statistical analysis, and am now confused about calculating the standard error of the mean. My dataset looks like.. Condition A: ...
2
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0answers
141 views

necessary condition for the existence of the posterior mean

I wonder if there exists results relating properties of the prior and the likelihood to the existence of the posterior mean (or more generally to the posterior moments). Any hint or sufficiant ...
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31 views

a question on posterior distribution

Suppose that $E[T]=E[\gamma_i|X_1]+E[e_2|X_1]$ (1) where $\gamma_i$ and $e_2$ are distributed uniformly on the interval [0,1]. $X_1= \gamma_i + e_1$ So the background is that im trying to find ...
2
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0answers
34 views

Estimating the mean from knowing the first n largest values

There is a sample of n values that are the first n largest values of a population. Is there a way of getting any statistic such as mean or dispersion from such piece of information provided that the ...
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0answers
24 views

Which mean centering approach is correct?

I have 2 possible ways to mean center. Take the mean of the training data only, and center both test and training data using it. Take the mean of combined test and training data, and center both ...
4
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1answer
82 views

Sum of products in an expected value

A box contains $n$ balls numbered from 1 to $n$. Suppose you take a ball at a time, putting it back on the box, until you pick a ball twice. How many balls are you expected to take from the box? Let ...
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2answers
38 views

alternative formulas for standard error of a difference between two means?

I have a question that seems basic but I found two alternative answers online so I thought that I should ask for advice. I have an experiment where each subject makes decisions about target words in ...
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1answer
46 views

How to combine sample means and sample variances?

Given a set of data, assumed normally distributed from 1 to 19. And two subsets of that data, one with the numbers below 10, and one with the numbers above: ...
2
votes
1answer
49 views

Given the distribution of a variable X, what is the distribution of f(X)?

Suppose I know the mean and standard deviation of a (roughly) normally distributed variable x. Is there any way for me to calculate the mean and standard deviation of f(x)? The particular problem I ...
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0answers
15 views

Can I average samples in nested factor within-subject design if samples are from the same condition?

This question relates to one of my other questions: Split plot with nested factors ANOVA in R . I have subjects taking an experiment, where I have different ...
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1answer
38 views

How to analyse data from different subjects?

DESIGN: I have 4 laboratory mice (= 4 subjects). My factor is a condition with 5 levels ...
1
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0answers
18 views

Estimate normal distribution mean given standard deviation and samples [duplicate]

I have samples from normal distributions with the same mean but different standard deviations. I know the corresponding standard deviation for each sample. Is there a way to more accurately estimate ...
1
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1answer
63 views

I want to estimate the mean of a variable. I would like to reduce the SE by controlling for the noise introduced by another second variable

I have a data set with two variables, V1 and V2. V1 is a continuous variable, whereas V2 is a binary variable. I would like to estimate the mean of V1. V2 is known to be adding error to V1 (V2 being ...
6
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4answers
981 views

Should the mean be used when data are skewed?

Often introductory applied statistics texts distinguish the mean from the median (often in the the context of descriptive statistics and motivating the summarization of central tendency using the ...
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1answer
33 views

Regression and link function

Suppose we have $E (\log (Y)) = a+bx $ vs $\log (E (Y)) = a+bx $. Can $\exp (b) $ in both cases be interpreted as a geometric mean?
0
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1answer
13 views

What is the confidence interval if I compute the total number of bits based on the average number of bits in sampled bins?

Let's say I want to estimate the total number N marbles among M sacks of marbles. The marbles are assumed to be normally distributed. I can't count them all, so I decide to sample S sacks. I get ...
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1answer
15 views

how to find probability of uniformity of data

I was working on image processing where I have some list of pixel value eg:-[5,2,5,2,4,2,4,2,2,2] so I found mean as 3 and variance as 1.77778 My question is how to find the probability of data been ...
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1answer
45 views

Estimating an overall summary statistic (mean) for a value reported by ten published studies

Background I am writing a systematic review and meta-analysis of the association of exposure to X with the outcome Y. I have identified ten studies that report on this subject. This will be a ...