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

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12 views

bootstrapped standard error to make inference about difference of means

I have a variable showing individual wages and a categorical variable of their race (Hispanic, Asian, etc). After getting their means, medians and their respective standard errors for each group ...
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18 views

State the distribution of the time he has to wait for four customers to arrive. Sketch its density and calculate mean and variance of the waiting time [on hold]

Lim operates a long-distance taxi service from the central bus terminal in Kuala Lumpur to Seremban, a town 60 km away. Customers arrive at his taxi stand at an average rate of one every four minutes ...
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1answer
46 views

mean of repeated measures…spot the (matlab) error

I have a population of 114 subjects. For each subject I have repeated measurements (1 each day) of the variable assessed (activity level). The number of measures varies for each subject (number of ...
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2answers
44 views

How to interpret the means of different sample sizes

I have three sets of data I am working with. The N of each are all vastly different and the means are also very different. I obviously don't want to interpret it so black and white because I know the ...
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5 views

Marginal means confidence interval

lets say that I have 4 groups and I want to report whether there are significant differences between them in a measured variables. Each group has different numbers of male/female and different ...
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21 views

least square mean

Here I read that when comparing groups with different characteristics (age, percentage of males, body mass index) means should be corrected for such imbalances. These corrected means are called ...
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8 views

Recalculating mean, median, std dev and confidence interval after updating sample

I am working on an application which gets rolling samples of World of Warcraft auctions every two hours. The auctions contain, among other data: item ID (will be used to group auctions before ...
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27 views

eigen problem of random matrix

Suppose I need to find the eigen vectors of a matrix $M(X)$ for any sample $X$ to be my dimension reduction projector. Then since I have samples $X_1,...,X_n$, so we propose to use the eigen vectors ...
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1answer
20 views

Comparing two samples, same mean but diferrent size and variance

I have two samples drawn from different distribution that I can assume the normality and the same mean for both, however, the variance and the size of samples are different. How can I compare the ...
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13 views

How to take median of medians when not all are weighted the same

I've got an arbitrary list of U.S. counties, with a median income score for each one. I need the median income of all of those counties together. (I could settle for an average if need be.) I've ...
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1answer
30 views

mean and standard deviation from rnorm(5, mean = 0, sd = 1)

I am trying to figure out a good way to find mean and standard deviation from sampling rnorm(5, mean = 0, sd = 1) 1,000 times. I thought about using a for loop and combining the result of rnorm as a ...
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11 views

What type of ANOVA for my experiment?

So I've got four different groups of participants and they have to rate faces which have been manipulated in four different ways, A, B, C and D. I want to compare the mean ratings between ...
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19 views

What type of ANOVA do I need to use?

At least I think it's ANOVA I could be totally wrong... I have two different groups of participants and four different types of faces. I want to compare the mean rating for each type of face ...
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1answer
49 views

What is the standard error of the mean of multivariate normal distribution?

Assume that the non-diagonal elements of the covariance matrix are not zero. Please provide a closed form formula. I'm interested in the bivariate case in particular. How does the formula simplify in ...
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1answer
46 views

How do you calculate the standard deviation and error for a difference between two different means?

I have 40 people that I measure at baseline, getting their mean level of X at time zero. I also calculate the standard deviation and standard error of the mean of X. Then after 100 days I measure ...
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0answers
21 views

Variance as a function of the mean. Why does this affect linear regression? [duplicate]

I'm currently studying university level statistics and I'm struggling to wrap my head around the concept of variance as a function of the mean. How does this affect linear regression and why does it ...
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0answers
36 views

How to determine stationarity, mean and covariance?

I'm having some trouble with some questions for an assignment that I need to do. The question asks to determine whether or not a process is stationary and if it is, what is its mean and covariance. ...
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0answers
26 views

Given the mean and standard deviation of a change, when can we expect to reach a threshold?

Suppose I am playing a game in which I start with 1000 points and my point total changes every turn. I lose when I reach 0 points. I know that after every turn I can expect that my point total will ...
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1answer
31 views

Modify standard deviation with fixed mean

I have a set of pipes that are supposed to receive balanced load from a source. For instance, with 100 of inputs if I have 5 pipes each is supposed to handle 20. But that's not the case in reality and ...
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2answers
50 views

Confidence interval of ratio estimator

As an example, consider a program that executes on two computers, A and B. Measuring the execution time of 3 executions each shows the following results: System A: 10s, 10s, 4s System B: 8s, 8s, 2s ...
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45 views

What is a test that I can use to determine if a time series is first-order stationary?

I need to test that one of the time series in my analysis has a constant mean over time. Is there a standard test I can use to help me determine this? I know that I can use a nonparametric procedure ...
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1answer
22 views

Possible to estimate distribution around mean given #samples, mean, highest and lowest?

For a project for which there are multiple bidders, the following is known: Number of bidders: 24 Mean bid: 104 Highest bid: 356 Lowest bid: 20 Given the above, is it possible (however roughly) ...
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1answer
38 views

RBF transformation on a Normally Distributed Random Variable

I have a random vector $\mathbf{X} \sim \mathcal{N}(\mathbf{m,\Sigma})$ which is transformed by a Gaussian Radial Basis Function into the random variable $\mathbf{Y} = K(\mathbf X) = \exp(-\lambda ...
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1answer
67 views

If I have means and medians, is there a way to average them?

Please consider these data points as an example of many more, they represent single studies with multiple samples which have been done during the last decades. ...
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37 views

Different Central Tendency Measures for Describing Groups or Individuals

Background: I have records with various metrics for many users. I want to develop a profile for each and also group similar users using clustering. Question: When developing a profile for each user, ...
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1answer
14 views

Calculating new averages

I'm studying for a midterm in my basic stats course and came across a question that I'm confused with how it's solved. A manager at a local gas bar has 13 staff members. The average hourly wage for ...
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43 views

Standard deviation of sampling distribution of mean

If we take a sample and calculate the mean, we can calculate the standard deviation for the sampling distribution of the mean using this formula: $\sigma / \sqrt{n}$ But, how many samples do we need ...
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2answers
43 views

What does LS (least square) means refer to?

I have been reading clinical papers and recently come across the term "LS-means", referring to what seems to me as an estimation of some population's mean measure. Obviously, I know what "mean" refers ...
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37 views

repeated measures design of Analysis of variance (ANOVA) with mean not statistically significant and Standard deviation significant

The study area was sampled using a tessellation-based stratified sampling scheme. The area was divided into 50-m × 50-m squares, a point was randomly selected in each square. For each point, a ...
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9 views

Calculate mean and std dev from experiment - no formal params

I am a little lost on how to calculate mean and std dev from an experiment (simulation). I have run the simulation (10000 times) and it output a set of numbers (10000). Plotting a histogram, it gives ...
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1answer
19 views

Unit of Mean and Standard Deviation

can a unit be associated with the mean and standard deviation values or these are "dimensionless" quantities? For instance, if I am computing distance, with unit being meters (m), and I have got the ...
5
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2answers
243 views

Just “take the average” they say. It's not that straightforward, right?

I have an acquaintance who does not study statistics and doesn't understand that summing data and dividing by the number of data is a summary statistic, i.e. that information is lost. For example, ...
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1answer
22 views

How to calculate standard error between means?

I would like to calculate what is $SE(\hat{x}-\hat{y})$ where $\hat{x}$ is the mean of the first sample and $\hat{y}$ is the mean of the second sample. I know the answer should come out as ...
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2answers
110 views

Ratio of standard deviation to mean

Let's say that we have a confidence interval like this: µ ± σ, where σ is the standard deviation and µ is the mean. I want to know if the ratio σ/µ has any interpretation? Does it mean anything if we ...
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52 views

Sort mean values with deviation

I'm trying to determine what physical attributes of a syllable are important in determining stress. So I have some recordings from different people saying a word, each person multiple times. And for ...
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25 views

Generate means and std. dev. in a repeated measures ANOVA

I got a repeated measures ANOVA with two timepoints (i.e. variables A1 & A2) as within-subjects dependent variable, and variable B as a between-subject independent variable. In the output (SPSS) ...
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0answers
10 views

A strange R limma voom function mean-variance trend [duplicate]

I am opening a long silent question here because I cannot understand my mean variance trend produced by limma. I am new to RNA-Seq analysis and tried using limma on my data. After voom transformation, ...
2
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1answer
37 views

Assessing deviation from the mean without Chebyshev's inequality

I have a set of experimental data which comprises distances between successive points: And a simulation which attempts to recapture the experimental data by choosing points at random and ...
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2answers
36 views

Average standard error

I have several measurements from the same population spanning over the course of several years, each year with its own mean and standard error (based on the same replicates at same location each ...
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0answers
49 views

4 cases of Maximum Likelihood Estimation of Gaussian distribution parameters

Let $x_1,x_2,...,x_n$ some normally distributed observations. So $\vec{x}=\begin{bmatrix}x_1 & x_2 & ... & x_n\end{bmatrix}^{T}$ In the context of my research I am trying to estimate ...
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1answer
66 views

Properly calculate mean and SE for meta-analysis

I want to perform a meta-analysis, for which I have data from 30 different experiments, each of them with two different treatments. I have three different types experiments based on how the data are ...
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27 views

What causes differences in estimates of 95%CI of the mean across subgroups in Stata?

In the small reproducible example, I'm calculating mean of a variable across three groups: ...
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0answers
20 views

Multiple DVs - MANOVA or multiple ANOVAs?

My project has multiple continuous DVs and a single categorical IV. When I run ANOVA for each of my DVs the means and SDs are different to when I use MANOVA. Why is that? Which one is correct? Which ...
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2answers
78 views

Averaging averages and standard deviations

I am comparing exam scores for different subjects: physics, biology, english. I am looking at what proportion of the curriculum is spent on each subject. The number of students is fixed: the same for ...
3
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1answer
119 views

How can I recreate a Weibull distribution given mean and standard deviation and the shape and scale parameters are unknown?

Figure 2 is a Weibull distribution of three different wind farms in Canada. These 3 probability distributions were combined in a study to obtain a common wind speed model. I will be using this common ...
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21 views

Comparing two data sets for a trend in the data

I have two data sets ( have only access to the statistics of data sets like mean, percentile, count etc but not the data it self). I am interested if I could have a metric which can answer below ...
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0answers
21 views

Regarding Bootstrap Hypothesis Test for difference of means, why not absolute differences?

Looking at the Algorithm 16.2 from "Introduction to the Bootstrap, Efron and Tibshirani" I was wondering why isn't the t(.) being tested the absolute difference of the means, instead of the ...
4
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2answers
53 views

Best way to test that one mean is greater than all the others

Suppose I have $k$ samples of different sizes, each of a different univariate variable. I want to test the significance of the hypothesis that the population of $k_0$ has a mean greater than all of ...
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1answer
12 views

Harmonic mean for averaging predictions?

I have 14 different predictions about each observation in my dataset and I want to compute an overall prediction for each observation based on these. Would it be better to use the harmonic mean ...
3
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1answer
62 views

Transformation among power-means

It is well-known that arithmetic and geometric mean are strongly related via logarithmic transformation, i.e. if we take arithmetic mean of logarithmic-transformed values we get the same as if we take ...