Questions tagged [mean]
The expected value of a random variable; or a location measure for a sample.
1,567
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7
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2answers
194 views
Independence of Mean and Variance of Discrete Uniform Distributions
In the comments below a post of mine, Glen_b and I were discussing how discrete distributions necessarily have dependent mean and variance.
For a normal distribution it makes sense. If I tell you $\...
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1answer
57 views
Central limit theorem and normal distribution confusion
So I'm trying to study for a test and I'm stuck on two textbook questions. I'm having trouble grasping the concept of sampling distributions and when to apply certain rules/when to categorize a ...
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1answer
26 views
How can I estimate the mean and standard deviation of the total duration of a family of tasks?
My current assignment at work deals with our in-house task system, which is largely responsible for executing operations and other work asynchronously from the usual HTTP request/response workflow. I ...
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1answer
13 views
Intuition for variance of mean sampling distribution
I'm having issues comprehending the reasoning behind the following formula:
For a sampling distrubution $$\overline{X_1}, \overline{X_2},..., \overline{X_N},$$
The following is true
$$ V(\overline{X})...
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0answers
16 views
Generating Data so that the Mean is a Multiple of 1/4 [closed]
I need to generate n numbers between 0 and 10 that are multiples of 1/4 AND I need to ensure that the mean of those n numbers is a multiple of 1/4. Can anyone suggest an algorithm to do this? ...
2
votes
1answer
39 views
Can a random variable/distribution have non-constant mean?
I have been asked that question, and it's very weird to me. I know how a random variable/distribution can basically not have a mean due to diverging integral of its expected value.
But how is it ...
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1answer
55 views
How to change exponential distribution into Normal distribution? [closed]
We have random data, which is exponentially distributed.
Data = exp($\lambda$), where $\lambda$ = 0.5.
If it is possible to change exponential distribution into the normal distribution. Then what ...
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0answers
23 views
Intuition behind standard deviation greater than mean for all positive values [duplicate]
I am following through this example
But it doesn't talk about what does it mean when the standard deviation is higher than mean when all values are supposed to be positive e.g. standard deviation of ...
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0answers
9 views
Is it possible to derive the median of a distribution from the mean and Gini Index?
I have some data on GDP, population, and the Gini index for various countries, and I would like to derive some median metric.
To put it more broadly, given the sum $\sum_{i=1}^{n} x_i$ and size $n$ ...
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0answers
27 views
Average of correlations over time
I currently work on my bachelor's thesis and analyse the correlation between 13 countries over a time period of 117 years. I built a correlation table and now want to say somethin about the average ...
0
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1answer
24 views
t-test with negative and positive variable values?
I have two variables (A and B) that are correlations, i.e. with values between -1 and 1.
I would now like to test whether variable A differs significantly from B. Can I use a t-test for this?
Or ...
0
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3answers
42 views
T-test for two independent variable
This image show sample taken from LA and NY for apple price. When I want to do a hypothesis test if the mean of NY price > LA price, I was saying that my NULL hypothesis is H0 : μ_NY - μ_LA > 0, but ...
0
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1answer
56 views
Why does the mean for a beta distribution when input into the scipy beta cdf not return 0.5? [duplicate]
Very likely I am missing some fundamentals here, or my python coding is not up to scratch.
When I use the standard formula to calculate the mean for a beta distribution ~ $B(\alpha,\beta)$
$$ \mu = \...
3
votes
2answers
454 views
Given mean and SD, can we approximate the underlying distribution?
I know the following info for values of a particular column for a dataset:
[mean=4.989209978967438, stddev=2255.654165352454, count=2400088]
Given just this, is it possible to approximate what the ...
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0answers
31 views
If Mann-Whitney U is a median test? Then what the heck is “unpaired pairwise median”?
Header: I am really sorry for the confusing title. I am going to edit it so it fits the responses I get based on Mann Whitney U.
So I had this exact question on stack overflow about is the Mann ...
2
votes
3answers
47 views
confidence interval for population parameters
This is my second question based on the understanding from this
suppose I want to estimate the mean height of all the students studying in 12th class in my state. I do not have access to the entire ...
0
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1answer
28 views
estimating population parameter mean and variance
I have a couple of questions, but I would go one at a time.
So what exactly estimates the population parameter.
I do not know the mean height and variance of my population, which is sufficiently ...
1
vote
2answers
35 views
Estimating population mean $\mu$ based on a sampling distribution
I've learned that under certain codnitions I can assume the mean of the distribution of sample means to be approx. equal to the real mean of the underlying population. Additionaly, the standard ...
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0answers
50 views
Sample Variance of Power of Sample Mean
I would like to know whether it is possible to derive a closed-form expression for the sample variance of the $n$-th power of the sample mean $\overline{x}_m$ that was calculated using $m$ sample ...
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0answers
17 views
% of samples below median with mean of sampling distribution and N?
I'm working on a homework problem and am unsure if this is a trick question. My understanding of the mean of the sampling distribution (μ_m) is that its used when ...
14
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1answer
1k views
What is the name for the average of the largest and the smallest values in a given data set?
What do you call a statistical mean that is calculated from upper and lower extremes in any given dataset?
For example, if you have a set:
...
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0answers
27 views
calculate the average visits and running days
What do I've got?
I have received a huge data from a real estate portal. It contains more than 50 million rows and data for over 10 years. In addition to the rental prices and other parameters (...
2
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1answer
27 views
Mean of a Poisson-Lognormal Distribution (PLN)
I would like to calculate the mean value of a PLN distribution,
$f(x;\mu,\sigma)=\frac{1}{x!\sigma\sqrt{2\pi}}\int_{0}^{\infty}\lambda_\ast^{x-1} e^{-\lambda_\ast} e^{\frac{(log(\lambda_\ast-\mu)^2}{...
2
votes
1answer
26 views
How to test significant difference of time-series data, i.e. the current data is significantly different from the past data
I am working on some data like below. The data have an increasing trend with big error bars. So what kind of statistical tool I can use to test if the current level of flux is significantly higher ...
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8 views
Difference between Autocorrelation of a function and stochastic average of the same function squared
What is the difference between < F(t)F(t') > - computed for all |t-t'| and <|F(t)|^2> - computed for all 't', conceptually, given F(t) is real and random? For simplicity, let us say Auto Corr of ...
3
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1answer
37 views
How to calculate standard error from a 95% confidence interval
I am conducting a meta analysis and one of studies doesn't have the standard deviation so i've been stuggling to work out the standard error. CI's are of 95%
I was wondering if I could calculate the ...
0
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1answer
51 views
Mean centering interaction terms
I want to mean center my interaction terms in a regression model (i.e., make the mean zero for each variable). I understand that I am supposed to mean center my variables first and then multiply them ...
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0answers
26 views
How data is normalized using mean and standard deviation
I think data with nomralized mean=0.5 and standard deviation=0.5 means all the data will range between (0-1) with mean 0.5.
But when I did the normalization I'm getting the values between (-1,1).
...
0
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2answers
28 views
two ways to compute average prices
I am doing some simple math computation. I have three variables: Goods, total price, and total unit (See below). All I wanted to do is to compute the average price per unit.
Method 1
I computed ...
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0answers
10 views
How to calculate variance of a data set with frequency spread over multiple years
If I have 4 books, with multiple copies of each book - [2,3,1,2 respectively], and I have 2 years data of these books.
Taking the example of book A, total number of issues of the book A in 2 years ...
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0answers
21 views
Determine a 90% CI for the mean of a new level of a variable
I have a dataset of time and temperature. There are 4 temperature settings and 6 measurements of time taken at each temperature. After a transformation, the data takes a linear form. I now need to ...
0
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1answer
67 views
Bayesian: learning about a normal mean and variance
OK, question edited in response to comment from @user158565 for those not in possession of the Jackman book. I tried to abstract the relevant information below.
I'm struggling with Simon Jackman's ...
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1answer
76 views
Should I compare the median or mean for my data?
I have a data frame in R that contains the information about 252 freshman university students.
...
22
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4answers
3k views
Why does mean tend be more stable in different samples than median?
Section 1.7.2 of Discovering Statistics Using R by Andy Fields, et all, while listing a virtues of mean vs median, states:
... the mean tends to be stable in different samples.
This after ...
0
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1answer
9 views
combined mean without population
I have been given data consisting of means and I would like to calculate the combined mean but I don't have population for none of them.
For example, the average exam score for 1st, 2nd, 3rd and 4th ...
2
votes
1answer
28 views
How do I sample N items from a list ensuring the samples are as similar as possible to each other?
Is there anyway to sample 6 numbers without replacement this list of 12 numbers
...
0
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1answer
10 views
Determining which methods to use to find how close a day is from the average pattern
Would anyone have advice on how to determine how close a day is to matching the average pattern of all days? I would like to take each day of the year and evaluate how close that day is from the ...
0
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0answers
28 views
Estimating population variance considering both population sample variance AND sampling method variance
I want to estimate the variance of a normally distributed population. I can take N samples and calculate the sample mean and sample variance, which would normally suffice; however, the sampling method ...
0
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0answers
22 views
Games-Howell Post-Hoc Test Results Not Expected
I ran a Welch's test in R to see if there were differences between my total deer density (deer per square mile) and the size of my reduction area (1, 5, 10, 15, 20, and 25 square miles). The summary ...
2
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0answers
26 views
Communicating aggregate percentage changes in data without exposing individual contributors
So i have a dataset that tracks widget production from 100 different factories, each individually owned and highly competitive. Each line contains the factory name, the date of production, and the # ...
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0answers
3 views
Sampling method to represent a larger demographic
I have a set of Google search queries for a particular user. Every query has its frequency, that is the number of times the person searched it for.
Now I have to infer some information about this ...
0
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2answers
53 views
Can the Median and mean be “zero”? [closed]
I have a data set with 32 variables. I take the summary of these variables. I found that some of these variables have a Mean or Median equal to zero. Is that Ok? Can I still work with this data set? ...
0
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1answer
29 views
Comparing means, having a large variance
Currently I am working on a project in which i do have two different sample-sets with a limited size and a large variance. Furthermore, I do have a bigger data-set that gives information about the ...
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0answers
10 views
Estimating yearly diagnosis rate from multiple studies
I want to estimate yearly diagnosis rates from some 8 studies. Each of the 8 studies contains the following data:
$n$ = total number of patients (e.g., 100)
$t_{start}$ = start timestamp of the ...
1
vote
1answer
22 views
standard errors for computing means via OLS regression
Suppose I have a variable $y_{i,t}$ which is say a well-being index for individual of type $i$ in month $t$. There are 2 types of individual, $A$,$B$, which are mutually exclusive, and three non-...
0
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2answers
34 views
Zonal statistics (mean± StDev) from polygons with different area
I am analyzing a temperature image using a land cover map with the overall goal to prepare a barplot where I report the mean ± StDev temperature for each land cover class. To do so I assigned each ...
0
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1answer
47 views
What is the relationship between: the first raw moment, location, expected value, mean in general, arithmetic mean for any sensible distribution? [closed]
I am a bit confused by the several sources telling that:
the first raw moment is by definition the arithmetic mean
expected value of any random variable is exactly the arithmetic mean
The expected ...
0
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1answer
15 views
What is the proper analysis to run when trying to compare means between multiple years?
I am trying to figure out the proper statistical analysis for my problem. I have a data set that has many variables but I am interested in how the mean deer density changes over time. I have multiple ...
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1answer
53 views
Mean and variance of a variable (inside a function) without known its distribution, but known mean & variance of the function
Let $$Z_k = A\, e^{i(2\pi B+\phi_k)}, \qquad k =1,2,3\dots$$ be a complex function with dependent on $\phi_k$ and others are real constants. Assume that the mean $\mathbb{E}[Z_k] = \mu_{z_k}$ and ...
1
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1answer
49 views
If I take mean of uncertain observations what happens to SD of the observations?
I have some observations, each with an accompanying standard deviation (shown here as error bars):
I want to make a summarised plot of this data by taking mean of all observations for a given X value,...
