The expected value of a random variable; or a location measure for a sample.
0
votes
2answers
227 views
Mean comparison for statistical significance
I was told to come here by a friend to ask a stats question.
I took Social Stats and Methods of Social Research about 4 years ago and to be honest, I don't remember much about it. Now I'm writing a ...
1
vote
2answers
138 views
Mean of a function of $K$ Gaussian random variables
Consider $K$ Gaussian random variables $Z_1, Z_2,\ldots,Z_K$ that are mutually independent with $Z_1 \sim \mathcal{N}(\mu,\sigma^2)$ and the remaining random variables $\sim \mathcal{N}(0,\sigma^2)$. ...
0
votes
0answers
63 views
Is there a closed form unbiased estimator of the median of n exponential variables from their mean? [closed]
Fix $n$. Suppose $T_1, \ldots, T_n \sim Exp(\lambda)$
For $n > 1$, is there ever an unbiased estimator of the median from a sample mean?
My attempt
$$\begin{align}P(median \le x) &= {K ...
0
votes
1answer
124 views
Show that $E(XY) = σ_{XY} + μ_Xμ_Y$?
Let X and Y be two random variables with means $μ_X$ and $μ_Y$ , variances $σ^2_Y$, $σ^2_X$ and covariance $σ_{XY}$ . Show that $E(XY) = σ_{XY} + μ_Xμ_Y$?
I tried the Covariance formula with:
...
2
votes
1answer
129 views
How is finding the centroid different from finding the mean?
When performing hierarchical clustering, one can use many metrics to measure the distance between clusters. Two such metrics imply calculation of the centroids and means of data points in the ...
0
votes
1answer
114 views
Plotting means and standard deviations
Does it make sense to look at a scatterplot of means versus standard deviations in terms of looking for outliers or changepoints? So the mean is on the x-axis and the standard deviation is on the ...
1
vote
0answers
52 views
Variance explained for averaged values
I am trying to work out how good my particular model is at explaining some observed data. The problem here is that the observed data takes the form of averaged (mean) values for each of my predictive ...
2
votes
2answers
86 views
finding mean and standard deviation
Experience raising Labrador puppies revealed that the weight of the puppies at six months follow a normal distribution. The subsequent weights (in pounds) of a small sample of seven six-month puppies ...
3
votes
3answers
692 views
R: Calculating mean and standard error of mean for factors with lm() vs. direct calculation -edited
When dealing with data with factors R can be used to calculate the means for each group with the lm() function. This also gives the standard errors for the estimated means. But this standard error ...
0
votes
0answers
65 views
Estimation of max likelihood sample mean and sample covariance
How do I estimate the maximum likelihood sample mean and sample covariance of the data set consisting of
N = 100 2-dimensional samples x = (x1 , x2 )T ∈ R2 drawn from a 2-dimensional Gaussian ...
1
vote
1answer
48 views
Average rate versus average period
I am working on a project where I need to do workload balancing, and to see how well my approach is working I want to compute both the average amount of time between requests for a workload and the ...
1
vote
1answer
142 views
Compare means of two groups with a variable that has multiple sub-group
I was unable to understand how to compare multiple mean values in each group. Within the subgroup the mean values influence each other (If one changes, the other changes automatically).
I collected ...
2
votes
2answers
120 views
Interpretation of an equation
I'm trying to describe the equation in the attached screenshot in my own words.
$\lvert(\overline\chi_1-\overline\chi_2)\rvert > s_1(t_{1 @ 99 \%}) + s_2(t_{2 @ 75 \%})$
The equation tests ...
1
vote
0answers
46 views
Assessing the consistency of an estimator of the average path length of a large network
I have found the following in a network-science article and would like clarification of what the authors are claiming:
We observe that the root mean square of the difference between the empirical ...
1
vote
0answers
76 views
Comparing many means in JMP
I'm trying to compare several sets of experiment data, by comparing means. I read there are several different tests such as Each Pair, Student’s t and All Pairs, Tukey HSD, which give different ...
2
votes
1answer
94 views
Normal distribution in R
I am trying to check what is the probability that a new observation is anomalous or not?
Suppose I have the following set of observations:
...
0
votes
5answers
192 views
How can I find distribution from mean and variance
If I know the mean and variance of a discrete random variable $\in \{0,1,\dots \}$, How can I find the distribution?
7
votes
5answers
383 views
If not a Poisson, then what distribution is this?
I have a data set containing the number of actions performed by individuals over the course of 7 days. The specific action shouldn't be relevant for this question. Here are some descriptive statistics ...
0
votes
1answer
44 views
What number minimises RMSD between itself and randomly generated numbers?
Let us assume that we have a random number generator given by its probability density function. Now, we need to use this distribution to generate a number that has the following property. It minimises ...
0
votes
0answers
65 views
What is a (rule of thumb) good signal-to-noise ratio?
Is there a rule of thumb for a signal-to-noise ratio that can be considered "good"?
In my case, for example, I got a signal-to-noise of 2.5, but in absence of a good benchmark I can't tell if this ...
6
votes
2answers
1k views
Mean absolute error OR root mean squared error?
Why use Root Mean Squared Error (RMSE) instead of Mean Absolute Error (MAE)??
Hi
I've been investigating the error generated in a calculation - I initially calculated the error as a Root Mean ...
0
votes
0answers
37 views
Calculate proportion among means with variance and CI
I have two groups of samples, with their own mean, SEM, CI.
I would like to calculate the proportion in percentage between the two. Rationing the means is easy but I don't know very well I should I ...
1
vote
2answers
127 views
What's the bar above x called in the sample mean?
What's the bar above x called in the sample mean? Is it a diacritic mark?
0
votes
0answers
35 views
Does the standard scores analysis make sense in the following scenario?
INTRODUCTION
I've got an image in grayscale.
Say the image is a rectangle with width = 1700 pixels and height = 2338 pixels.
The image is light in the middle and dark in the top and bottom edges.
The ...
0
votes
0answers
41 views
Comparing tests for staging cancer
I am comparing 4 different tests for the evaluation/identification of cancer. One is a continuous variable yielding cut-off values based on both the mean and the median of 5 consecutive measurements ...
3
votes
2answers
248 views
does it make sense for non-negative data to subtract the mean and divide by the std dev?
It is a very usual procedure to subtract the mean and divide by the standard deviation in a set of data. If we deal with non-negative data, i.e. image, (in [0,1] or [0,255]), does this procedure make ...
0
votes
0answers
47 views
Compare variability in different groups
I have 3 groups with a distribution of samples. I used ANOVA to compare means of these groups and also fetched mean, SD and SEM.
I have SD and SEM that varies among groups. How can I compare them so ...
3
votes
1answer
328 views
Maximum likelihood of function of the mean on a restricted parameter space
I've been trying to teach myself some of the fundamentals of statistics by trying to work through old qualifying exams. Here's a problem:
Suppose $X_1, \ldots, X_n$ are a random sample from a normal ...
0
votes
0answers
91 views
How to do a difference in means test for panel data?
I have panel data (5 variables) and binary outcomes (died, survived) for same individuals over few years (quarterly data).
If it wasn't panel data, it would be easy to perform "difference in means" ...
0
votes
1answer
41 views
How to remove individual means and deviations for repeated measures
I currently have a experiment with a within subject design, where I repeatedly measure reaction times (RT). Reaction times for each category of reaction were measures multiple times. However now the ...
2
votes
1answer
233 views
Correlation with binary response and Likert scale response
I have 4 data groups:
- 3 groups from a 5-point Likert scale (1 ~ 5)
- 1 group is binary (Incorrect/Correct -- converted to 0, 1)
I have performed Pearson's r and Spearman's rho with the Likert ...
3
votes
2answers
256 views
What is the equation for combining standardized mean differences across multiple studies?
I am trying to come up with a combined/pooled standardized mean difference for meta-analysis of a dozen or so studies that have the same binary predictive groups and the same continuous outcome ...
0
votes
1answer
297 views
Transform Data to Desired Mean and Standard Deviation
I am looking for a method to transform my dataset from it's current mean and standard deviation to a target mean and a target standard deviation. Basically, I want to shrink/expand the dispersion and ...
0
votes
1answer
72 views
How large a variance can be for a discrete random variable whose mean is known?
In following Maximum value of coefficient of variation for bounded data set
I come up this question:
e.g., Say, $X$ can take integer values from $[0, 20]$
The mean of $X$ is known to be $0.005$
What ...
1
vote
0answers
14 views
Best way to characterize slowdown factor
I am currently measuring the execution time of a program I have written, but I am unsure how to represent the results. The program has two modes: normal mode and analysis mode. In analysis mode, it ...
0
votes
0answers
78 views
Statistical tests affected by the mean values of the two samples
The experiment consisted of this :
31 devices of type $A$
26 devices of type $B$
All the 57 devices were side by side in order to measure the level of ambiant radiation.
So, I have the doses for ...
2
votes
2answers
116 views
Comparing means across sub-groups?
Bit of a stats newbie question here. I've got about 10,000 rows of data about pupil performance, annotated with school and teacher details, that look as follows:
...
1
vote
1answer
61 views
Estimating conditional mean
Suppose I have a uniform random variable $X$ taking values $\{1,...,n\}$, and two functions $v(X)$ and $w(X)$.
I know that $v(X)$ and $w(X)$ are jointly distributed with correlation $\rho$.
(And can ...
1
vote
1answer
222 views
How to test whether the difference in difference between means is significantly different? (with example)
Basically I have
Four groups (2-by-2) with sample means $\overline{x_{1,A}}$, $\overline{x_{2,A}}$, $\overline{x_{1,B}}$ and $\overline{x_{2,B}}$, standard deviations $s_{1,A}$, $s_{2,A}$, ...
4
votes
2answers
175 views
Finding mean when class sizes are unequal
A class teacher has the following absentee record of students:
...
1
vote
1answer
121 views
An analytical framework for considering the geometric mean
Is there an analytical method of looking at the geometric mean that will allow one to break it down to its various components?
The focus of the question is more for financially related returns, but I ...
4
votes
1answer
66 views
nth moment, for 0 < n < 1 or n <0, do they exist?
I am interested in the moments, we have for instance the mean, E(X) and E(X^2). what about values like $E(X^{1.5})$ or $E(X^{-1})$? Have they been investigated?
2
votes
1answer
96 views
How to estimate the probability that the mean of an unknown distribution is over a threshold given small sample size
I am trying to quantify my concerns regarding a proposed incinerator in our community. The company is basing its potential to emit dioxins (a class of chlorinated organic compounds with a reference ...
0
votes
0answers
77 views
Compare independent numeric vectors (means) in R
I am working on R, and have multiple data.frames. They all look like this one:
...
0
votes
1answer
47 views
How do you take a weighted mean where values farther from a given number are weighted less?
Say, I have a vector v = {5,2,8,9,2}
I then want a weighted mean where values of v closer to a given number (which could be mean(v), or something else) are weighted more (proportionally). So 5 (or ...
0
votes
1answer
295 views
Sum(XY) in terms of Xbar and Ybar [closed]
If $x$ and $y$ are two series, is there any relation between $\sum{(x,y)}$ that can be expressed in terms of mean of these two. Specifically, I want to know if any sort of relation exists between ...
1
vote
1answer
334 views
What formula is needed to calculate the average adjusted gross income by zip code?
Here is an example of one zip code I'm working on:
A00100 is the Adjusted Gross Income (aka AGI), agi_class is the size of the adjusted gross income. This ranges from 1 to 7:
...
0
votes
1answer
192 views
Weighted harmonic mean vs weighted geometric mean [duplicate]
Possible Duplicate:
Weighted geometric mean vs Weighted mean
I searched for the differences between WHM and WGM.
When to use each of them? when not?
2
votes
0answers
64 views
Is ANCOVA proper for my experiment?
I've got a serious problem when trying to analyse the data of my psychological experiment. Here are the details of the experiment:
In each trial, subjects were presented with lateralized colored ...
2
votes
1answer
245 views
Harmonic mean with zero value
How does harmonic mean handle zero values? what would the harmonic mean of {3, 4, 5, 0} be since $1/0=\infty$?
