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

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23 views

Splitting the Standard Deviation into groups

I have a set of data for which I have calculated the mean and its standard deviation. Based on the standard deviation, I'd like to group that data as one of the three : High standard deviation, ...
0
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1answer
15 views

Using the average as a cut off to group data and compare groups?

I measured cell size of human muscle and I wanted to examine the effect of age on the parameter. I graphed my data as a scatter plot and calculated Pearson's correlation coefficient but then also ...
0
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0answers
18 views

Time-partitions of sample size

I am struggling with explain something I read in a Whitepaper. The essence is as follows. Let's begin with a random variable $X$ defined as number of events in an hours. Further, we assume that $X ...
2
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2answers
34 views

Which is better, replacement by mean and replacement by median?

I'm doing a project that involves replacing missing values in a set of data (first time doing this). This is involves using to methods "replacement by mean" and "replacement by median" to fill in the ...
0
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1answer
35 views

Mean vs. Standard deviation for data ranging between 0 and 1

If e.g. 100 people can rate a subject between 0 and 1 than the dispersion (e.g. standard deviation) among the 100 raters is potentially largest for a mean of 0.5 (50 people rate 0, 50 people rate 1) ...
9
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2answers
194 views

Does a prediction interval have to contain the mean?

I am having a huge problem with a conceptual problem that I came up with. Say a company has a distribution that is highly skewed. Something similar to an exponential or lognormal only more extreme. ...
0
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0answers
13 views

comparing time ratios

I have two different implementations of an algorithm and would like to compare their runtimes on test data. The test data consists of multiple instances. I run every algorithm on each instance and ...
2
votes
2answers
108 views

Which notation should be used for the mean, SD, and median: mean±SD or mean (SD)?

I usually use mean±SD notation for reporting values. I know that many people use mean (SD) notation and I understand why. Right now in the document I am writing I am also reporting medians but I ...
0
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0answers
10 views

Anova Post Hoc Test

I am running an anova in SAS on the average hours worked for a country. With those countries grouped into 3 regions. When I run the anova I get a F value of 3.64 and P-value 0.0379. With these ...
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0answers
14 views

Accuracy of reported measurements

I take three measurements: 71, 72 and 74. Each of the three measurements have 2 significant digits. The mean of my three measurements is 72.33 (rounded to 4 significant digits). Because my ...
2
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1answer
46 views

What is the relationship between the mean of a continuous variable and expected value?

What is the relationship between the mean of a continuous variable and expected value? How are they connected?
3
votes
1answer
33 views

Why is the CI in the median larger then the CI in the mean?

if I generate sample of normally distributed values (N=100, Mean of 10, STD 2.5) Then I calculate the mean with confidence intervals and the median with confidence intervals of the sample I get: A ...
0
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2answers
44 views

SEM Interpretation

Standard error of the mean (SEM) represents the accuracy of the mean. Here's my question/doubt. Does higher the SEM mean higher the accuracy of the mean? To be more precise, what indicates ...
2
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1answer
17 views

Non neglible instrument error associated with a mean

I have N samples, that have mean X and standard deviation sigma. So far so good. I know that each sample has been measured with a measurement error e. Because the data is real world data the ...
1
vote
1answer
34 views

Unbiased Estimators

So I've been banging my head against the wall trying to figure out where to go with these problems, and I'm looking for a little direction. Suppose that $Y_1, Y_2, Y_3$ is a random sample where the ...
2
votes
3answers
80 views

Standard error of a population

I measure the weight of 100 people and pick 20 lots of 5 people from these 100. Therefore n = 5, repeated 20 times. The 100 people represent the population and groups of 5 people represent samples ...
-1
votes
1answer
33 views

Binomial distribution [closed]

folks! The problems is Suppose you can make free throws at a 70% rate. Let X be the number of free throws you make in 20 tries. Model this with a binomial distribution: 1)?= E[X] 2)?=Var[X] ...
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votes
1answer
39 views

What is the Mean Squared Error for this estimator?

I understand that to find the MSE, i must find the variance and bias and add them together. I've had trouble calculating either of these so a breakdown would be immensely helpful. The estimator is: ...
1
vote
2answers
52 views

The meaning of scale and location in the Pearson correlation context

According to wikipedia, pearson correlation is scale and location invariant. Does scale refer to "variance" and location refer to "mean" ? Thanks.
1
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2answers
27 views

How should I determine an average from a set of averages

I have a set of lines. I measure their length each 5 times, and then take the mean of their lengths (as I measure them). I also take the standard deviation. I want to know the 'average' line length. ...
0
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0answers
45 views

mean of log or log of mean

I'm interested in how indiviudals are influenced, by other individuals they are connected to. So mean values of connected individuals are included in a linar regression model. Some of my variables are ...
2
votes
1answer
48 views

Distributions with Median=Mode=Average?

Is there any important distribution with Median=Mode=Mean, apart from the Gaussian and Student's distribution?
0
votes
1answer
33 views

Trimmed mean vs median

I have a data set with all the calls made to an emergency service and the response times of the ambulance department. They admitted that there are some mistakes with the response times as there are ...
0
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1answer
21 views

How to compare the means of two populations that were subject to five treatments?

I have two populations that were each subject to 5 different treatments and I want to compare their means. This sounds like a great problem for multiple confidence intervals, but I don't want to make ...
1
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1answer
35 views

SPSS ANOVA or MANOVA or huh?

Me again asking the silly questions - this might belong here as I've been told it may belong in a software section somewhere..? Which I have still been unable to find. Here is a screenshot of my ...
5
votes
2answers
94 views

Can the difference between the means of two groups lie outside the confidence interval for the difference?

I received this question from a colleague which left me with a desire to find out a bit more about it. If you have two groups A and B with means--for example, 7.9 and 5.8--is it possible that the ...
0
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0answers
23 views

R limma voom function trend in mean-variancerelationship

I am new to the Limma package and when using voom I get this. I am really not sure what it means. I wonder if anyone here have seen something like this before, or ...
0
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1answer
42 views

Question about probability of 0.99 that an average lies less than L years above overall mean

The duration of Alzheimer’s disease, from the onset of symptoms until death, ranges from 3 to 20 years, with a mean of 8 years and a standard deviation of 4 years. The administrator of a large medical ...
1
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1answer
36 views

Beta binomial mean different from actual mean

I have data that I am fitting a beta binomial distribution to. The VGAM package for R is being used to do this. However, the the mean of the fitting beta binomial distribution is vastly different from ...
0
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0answers
7 views

Calculating average fuel consumption with no complete data

Background I just answered a question about SQL on StackOverflow, but think there's a more important question about statistics which I'm unqualified to answer. The asker has 3 fields: f - Fuel ...
1
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0answers
17 views

Calculating the highest of overlapping sets

My data set looks like the following: I have information about a large number of devices. For each device, I also have the data consumed by an application per day. Note however, all the devices ...
0
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0answers
14 views

Choosing the right bins - 2d to 1d radial average with correlations

I have a 2d array of data. I want to take the average of the values in radial bins, the average is dependent on radial distance (Basically dealing with the 2d Power Spectral Density from and Image and ...
18
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6answers
524 views

Is the median a type of mean, for some generalization of “mean”?

The concept of "mean" roams far wider than the traditional arithmetic mean; does it stretch so far as to include the median? By analogy, $$ \text{raw data} \overset{\text{id}}{\longrightarrow} ...
5
votes
2answers
53 views

Reporting Results of Mann-Whitney U Test - Means vs Medians

I had a question yesterday that I got a bunch of great responses on. I have, hopefully, a quicker question here. There is a debate in the literature regarding reporting means vs medians in a ...
1
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1answer
112 views

2 discrete distributions with equal mean and variance

I need to compute 2 discrete distributions with equal mean and variance. One should be a distribution taking values x and y and the other one taking values z, 0, and y. The probabilities should take ...
7
votes
1answer
610 views

Which converges faster, mean or median?

If I draw i.i.d. variables from N(0,1), will the mean or the median converge faster? How much faster? To be more specific, let $x_1, x_2, \ldots $ be a sequence of i.i.d. variables drawn from ...
3
votes
2answers
89 views

How to properly state the average of a discrete number in a report?

I'm wording a report on the averages of a discrete variable, and am trying to get the most appropriate sounding wording. Consider the able below: ...
8
votes
1answer
210 views

Displaying Ordinal Data - Means, Medians, and Mean Ranks

Thanks in advance for any help. I have some ordinal data that is not normally distributed, so I decided to do non-parametric testing using the Mann-Whitney U Test. I am looking at differences ...
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votes
1answer
86 views

Calculating mean and variance of normal distribution restricted to interval

If one set a lower and an upper limit on the normal density, is it statistically valid to calculate the mean and Standard deviation of that normal variate. If yes, how can we do that in R? In a more ...
1
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0answers
28 views

Generate discrete distributions with same mean and variance

I have a question concerning mean-variance analysis. I need to compute 2 discrete distributions with equal mean and variance. One should be a distribution taking values x and y and the other one ...
4
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1answer
28 views

Is this method of arriving at a statistic valid?

The following is an excerpt from an article about gender bias : Overall, 34 per cent of respondents readily admitted that their family preferred having more boys. Given the sensitive nature of ...
0
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0answers
17 views

Calculate mean of several tetrachoric correlation coefficients

how do I calculate the mean of several tetrachoric correlation coefficients? Do I have to use Fisher's z transformation before? Thank you
0
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0answers
30 views

Gaussian or Dirichlet Process from aggregated samples

For N individuals, I have the number of measurements taken per individual, the individual's mean measurement value, and the standard deviation of the individual's measurements, but I do not have ...
2
votes
2answers
72 views

Mean Preserving PDF Spreading

I have a histogram representing the PDF of an unknown discrete RV. The histogram is asymmetrical. To be clear, all I have is the histogram. Is there a known way to increase/decrease the variance of ...
1
vote
0answers
31 views

Mulitvariate normal truncated conditional expectation

There is three-variable multivariate normal distribution. Denote 3 variables with $X_1$, $X_2$, $X_3$. Let $\mu_i$ be means, and $\sigma_i^2$ variances of respective variables, and let $\Sigma$ be ...
0
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1answer
36 views

Find new mean from Normal probability

I have a problem as follows. Life of tyres normally distributed for a specific make. mean=24,000 km and sd= 2500 km. Question is: As a result of improvements in manufacture, the length of life is ...
1
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1answer
27 views

Compare means of group with a mean of a subgroup

It is possible to compare a variable, for example age, between an entire group of patients and a subgroup of patients (a part of the entire group)?
5
votes
2answers
178 views

Arithmetic or geometric mean to calculate an annual average price index?

I have monthly indices (Consumer Price Indices for 12 months) for a set of countries. I want to calculate the annual average for each country in order to have an average Consumer Price Index for a ...
1
vote
1answer
33 views

Comparison of two means within the same group

I created a pretest before my main study. The goal of the pretest is to find two brands that are equal in terms of liking and familiarity. I computed the variables in SPSS and I was wondering if I ...
1
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0answers
27 views

Should I use arithmetic or geometric mean here?

So I have monthly indices (Consumer Price Indices for 12 months) for a given country. I want to calculate the annual average for each country in order to have an average Consumer Price Index for a ...