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

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3
votes
1answer
59 views

Why is the mean of a Chi Square distribution equal to the degree of freedom?

Is this part of the definition of a Chi Square distribution? Or is it deduced from another property? In which case, what is the proof?
0
votes
2answers
48 views

mean of the product of n dependent indicator random variables

How can I simplify $E( I_1*I_2*…*I_n )$, which is a mean of the product of n dependent indicator random variables. Can I write down something like $E( I_1*I_2*…*I_n )$= $E( I_1)*E(I_2)*…*E(I_n)+Cov$ ...
2
votes
0answers
47 views

Probability than empirical mean of one binomial RV smaller than another

Lets suppose I have two binomial random variables: $X \sim B(n_1, p_1)$ and $Y \sim B(n_2, p_2)$. I would like to calculate the probability than the empirical mean of $X$ be smaller than the empirical ...
6
votes
2answers
97 views

Estimate of parameter of exponential distribution with binned data

I have the following data, which can be modeled by exponential distribution ...
1
vote
0answers
15 views

Comparing different scale ranges for one Likert scale instrument

I don't believe this exact question has been asked before. I am conducting a meta-analysis on a certain Likert scale survey instrument that has been psychometrically validated. It is a 16 question ...
3
votes
0answers
25 views

How do I generate appropriate group-level coefficients and standard errors for my regression?

I ran a mixed logistic model testing the influence of group (two-level) on a binary outcome, and I want to report the group estimates and their SEs in graph. However, I can think of two ways of doing ...
0
votes
0answers
5 views

Weighted mean / average where you reward the lowest value / cost / distance

Best I've several weather-station (200), placed across the country (508 municipalities). Now, I would like to prescribe the weather info, e.g. temperature, to each of the municipalities of that ...
1
vote
1answer
32 views

What mean should be used for the variables that are involved in a linear regression model in a log-transformed space?

This has been bothering me for a while. Both $X$ and $Y$ are material properties. They can be described using a linear regression model built in the log-transformed space, i.e., $\log Y=a \log X+b$. ...
3
votes
1answer
52 views

How does one go about determining the standard deviation of an entire sample data set?

I have frequently been faced with analyzing csv files that are limited in length to approximately 32,000 records in length (overflows at 32,768, from signed integer limits on a 16 bit wide data bus). ...
7
votes
3answers
456 views

Is it valid to derive a mean from categorical data?

I am working on a study to quantify average working hours for doctors. However, when I leave it empty for respondents to fill up, it remains unfilled. Changing it into categories as above yield ...
0
votes
0answers
20 views

Classification of real values

I have values of attribute between 0 and 1 which i want to predict. The distribution of values is shown in fig. I want to predict this attribute. The problem is there are around 15 classes in this ...
4
votes
1answer
69 views

Maximum of a set of values from given mean and median

The arithmetic mean and median of $5$ distinct natural numbers are both $7$,what may be the maximum of the $5$ numbers? Here we see that the median is the $3rd$ value.Also the sum of the numbers is $...
5
votes
4answers
302 views

Should I use an average to summarize ordinal data?

I need to work out a "average" (for lack of knowing a better word) of ratings or perhaps I could call them labels. Basically, I have a list of words that have been rated 1 - 3 for difficulty. 1 being ...
2
votes
1answer
31 views

How to get a mean from multiple categorical fields

I have some census data on income I would love to analyze. But income, in the data, is split into different income groups, each group is a column containing the number of people in an area that earns ...
2
votes
0answers
15 views

Higher variance in sample mean or sample median? [duplicate]

The variance of the sample median depends on the distribution you are sampling from. This is also true for the variance of the mean. But can one say that the variance of the sample mean is always ...
1
vote
3answers
19 views

What statistical method should I use to filter out the correct point?

My project is in the field of image processing. The output of a certain program would print the x and y coordinates in the image. I calculate the arithmetic mean of the points to get the mean ...
0
votes
1answer
29 views

Inference about two samples

I have two different large samples, one is normally distributed (0,1) and the other one follows a t-distribution (df = 4). Can I compare whether the means or the st. deviations of both samples are the ...
1
vote
0answers
19 views

Weibull, Gumbell and Extreme Value: from mean and variance to shape, scale and location parameter

I need to sample random numbers from Weibull, Gumbel and Generalized extreme value distributions. Of all of these distributions I know mean and variance. My question is: how can I determine these ...
0
votes
2answers
23 views

Co-Variance of Zero and Non-Zero mean random variables

Is the value of co-variance function for non-zero mean random variables different from the value of co-variance function when random variables have a zero-mean? I think yes based on this: For a ...
0
votes
0answers
16 views

Standardized difference of means for multiple classes

Standardized mean difference is very straightforward when you have 2 distributions / groups. How is this metric computed when you have >2 groups? Is there a better alternative to determining the ...
0
votes
1answer
31 views

Calculating Standard Deviation of the Volume of a Cube

Let's say I have a machine that makes cubes. My goal is to determine the average and standard deviation the volume of a cube. I have N length, width and height measurements. I do not believe these ...
0
votes
0answers
14 views

What n to use for significance of correlations in three different scenarios

I feel these questions might already be answered around here somewhere, but I was not able to find it, so here goes. 1) General case of time-series When determining the significance of a correlation ...
0
votes
0answers
18 views

panel data mean and standard deviation

I have panel data of the form $r_{it}$ i.e. I have repeated observations of the random variable $r$ varying over individuals (i) and over time (t). Let's assume I compute the grand mean and sd of ...
1
vote
1answer
37 views

Robust statistic for representing small dataset with outliers and representing them graphically

I'm evaluating different systems varying a certain parameter common to all of them. Let this parameter be x. At each x value I ...
1
vote
1answer
23 views

Calculating speedup confidence interval

Summary I'm trying to calculate the confidence interval for speedup of a program when I have many measurements for the old and new execution times. Details Speedup is calculated as: $\frac{time_{...
0
votes
0answers
23 views

Variance of subsample?

Total sample = subsample 1 + subsample 2 I have the mean and variance of total sample and subsample 1. I have n for total, subsample 1 and subsample 2. I can calculate the mean of subsample 2 ...
0
votes
0answers
13 views

Combine multiple means and upper/lower standard deviation values

I need to combine the means and upper/lower 1 sigma values for three different estimates of the same parameter. For example, a given set of means (m) and upper/...
2
votes
0answers
26 views

Comparison of two means when they are means of means?

I have two vectors "A" and "B". Each vector contains multiple mean values derived from observations. The two vectors are subsets of a sample that has been categorised into five vectors. All vectors ...
0
votes
0answers
30 views

mean\medians as data points in two way repeated measures ANOVA

I have a table with 12 columns each regarding one combination of three (2X2X3) diffrent conditions in an experiment. Each row (25) represent a subject that did the experiment. Each data point in the ...
0
votes
0answers
54 views

What is zero mean and unit variance in terms of image data?

I am new to deep learning. I am trying to understand some concepts. I know "mean" is an average value and "variance" is deviation from mean.I have read some research papers, all say that we pre-...
1
vote
1answer
50 views

Confidence intervals for group means (R)

Here are some sample data in R: set.seed(42) df <- data.frame(g = factor(rep(1:2, each= 50)), y = rnorm(100)+rep(0:1, each=50)) One can easily get group means ...
3
votes
1answer
56 views

Negative variance result when calculating standard deviation

Please note, I am still in secondary school so please keep your answers simple. A question on my homework states to calculate the standard deviation from a given frequency table with several class ...
-1
votes
1answer
37 views

Sample mean and sample variance [closed]

The sample mean is $\bar X = \frac{1}{n}\sum_{i=1}^n X_i$ and the sample variance is $S^2 = \frac{1}{n-1} \sum_{i=1}^n (X_i - \bar X)^2$ Can someone please explain how the sample mean and sample ...
0
votes
0answers
46 views

How to calculate Mean and Standard deviation in Lognormal distribution where only P90 and P10 are known

I have P90 and P10 of a lognormal distribution. P90=142.56 and P10=3415; I need to estimate the mean and standard deviation of this lognormal distribution. I have done the following steps and then ...
1
vote
2answers
178 views

The average of mean and standard deviation

I have the mean and standard deviation for body temperature ( in a group of people n=10 ), which measured using a thermometer in the left axilla, then in the right axilla ...
3
votes
1answer
70 views

How do I find the expected value of F(isher)-distribution

$E(F)=\int xf_{k,m}dx$ where $f_{k,m}(t) = \Gamma(t)=\frac{\Gamma((k+m)/2)}{\Gamma (k/2)\Gamma(m/2)}k^{k/2}m^{m/2}t^{k/2 - 1}(m+kt)^{-(k+m)/2}$. How do you find $E(F)$? Say you have to convert $x*f(k,...
3
votes
1answer
40 views

When confidence intervals of two parameters do not overlap with the mean of the other, why is it considered to be statistically significant?

Consider two parameters with means A and B with 95% confidence intervals. If the confidence intervals of the parameters do not overlap with the mean of the other, why is it considered to be ...
-1
votes
1answer
31 views

Learning Statistics [closed]

I am new to statistics and I am trying to get my head around 'why' some of these are calculated the way they are and what they mean, or were they just made a preference that stuck? - the statistics ...
1
vote
0answers
30 views

ANOVA : mean or variance?

I am confused about the ANOVA method in Statistics. ANOVA stands for analysis of variance. It is used to compare the mean between several groups. We use a test of variance (Fisher) for ANOVA. So, is ...
5
votes
2answers
299 views

What does it mean to say that “the population mean is a single fixed number?”

I am trying to figure out what it means if a population mean value is fixed.
0
votes
0answers
32 views

Good algorithm to compute the sample mean and variance [duplicate]

I am looking for good (fast, memory efficient, ideally one-pass) algorithms to compute the sample mean and variance. I have found a technical report by Chan, Golub, and LeVeque from 1983 with ...
0
votes
1answer
22 views

Test for significance of peaks (maximum) in time series

I have a time series of values, something like this: ...
1
vote
0answers
20 views

Cross correlation of gaussian signals with its mean signal gives non-gaussian distributed scores

The following is my question: I have signals that contains noise, they are of the following form see the figure below.. Then I take the mean signal of all these signals (identical in length and shape)....
1
vote
0answers
29 views

Probability of Non-exceedance modelled by Normal Distribution Question

The complete question is: A number of pre-cast beams are to be laid side-by-side to form a bridge deck which will later receive an in-situ topping. The beams are nominally 300mm wide, but in practice ...
0
votes
0answers
20 views

Outliers detection or some roubust metrics on long tail sqewed distributions

I have a distribution of user sessions on the web site in the following format date,sessionId,price 2010-01-01,1,0 2010-01-01,2,0 2010-01-01,3,10 ... And I am ...
0
votes
1answer
30 views

Measure of Central Tendancy in ARIMA?

I know very little about the ARIMA - the AutoRegressive Integrated Moving Average - model but I am interested in what type of central tendency is represented by "average". Is it simply the mean? If so,...
1
vote
1answer
24 views

Measuring forecast accuracy of the conditional mean

Consider a dependent variable $y$, independent variables $x_1,\dotsc,x_K$, a model $$ y = X \beta + \varepsilon $$ and an estimated coefficient $\hat\beta$. If the model is assumed to be well ...
1
vote
1answer
30 views

Compare several means with different sample sizes (greater than 2)

I have seven different groups with different sample sizes and variances and I want to compare the means of their data. I'm not very informed in statistics, so could anyone help me out here? I've only ...
0
votes
0answers
35 views

Anova Profile Plot - Estimated Marginal Means understanding

I would like to ask you a question with regards to the Profile Plots generated by SPSS for 2x2 ANOVA (with balanced design). I have two Independent Variables, each one with 2 levels, and a Dependent ...
0
votes
1answer
23 views

Can one calculate a general mean for questions that use different scale length?

I have two sets of questions: 1). 5 questions with answer options from 0 to 10 (very unsatisfied to very satisfied) and 2). 9 questions with answer options from 1 to 6 (same meaning) The study was ...