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

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2answers
52 views

Comparing normal with non-normal

I have two sets of data for setup time of a machine, one is setup time when fixture is running alone, another is when another fixture is running alongside. For fixture running alone the data I ...
-1
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0answers
15 views

frequency distribution and mean and mode [closed]

According to a report regarding the weekly earning of 1000 employees of a firm, the earning of 4% were under Rs. 300 and those of 15% were under Rs. 315. 15% of the workers earned Rs. 475 and over ...
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0answers
15 views

Mean in Cumulative frequencies distribution

Monthly expense Cumulative Freq. up to 50 7 up to 80 25 up to 120 49 up to 200 58 over 200 60 Calculate ...
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1answer
21 views

Can Coefficient of Variation be used to verify the representativeness of the mean?

I have a sample with approximately 45 million elements, with 4,410 as the mean and 1,657 as the standard deviation. I am not confident whether or not the mean well represents the sample due to the ...
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1answer
14 views

Correlation on mean values

Please note: the variables named in this example do not correspond with actual variable type values, but are simplified for clarity purposes. I have 13 groups, each containing values X of, say, the ...
1
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1answer
38 views

Can I use z-scores in right skewed distributions?

I have a right-skewed distribution that represents that number of "likes" on a certain car category for a number of users. What I am trying to do is a sort of classification based on z-scores. For ...
0
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0answers
17 views

Testing if the mean of one data set is bigger than the mean of the other data set [duplicate]

I have two data sets, i.e., the number of flowers measured in field A and in field B. Each data set has about 40 samples. I want to do a test to check the hypothesis that field A has more flowers than ...
1
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0answers
11 views

Plotting raw data, but running statistics on log-transformed data

My data is non-normal, I want to show my raw data, in a scientific journal, by median +/- mad, to show the true nature of the data. However, if log-transformed, the data is normal. Can I then ...
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0answers
11 views

real time object tracking

I have correlation value of object using mean and standard deviation, now i want to normalized that correlation value. how can get normalized correlation in terms of percentage vale?
5
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1answer
123 views

$\bar{X}$ versus $\mathbb{E}(\bar{X})$?

I was not able to find this question here, so I am going to ask this: What is the difference between $\mathbb{E}(\bar{X})$ (expected value of $X$ bar) and the actual $\bar{X}$? I am very confused ...
0
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1answer
6 views

Best method of estimating the output rate of a group

I have a sample dataset consisting of 2 fields, output volume and input time (in hours) for different persons performing an identical task several times each. What is the best method of estimating ...
0
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0answers
11 views

Histograms With No Final Interval Upper Limit

If you have the following histogram, how do you calculate the mean if you do not know the upper limit of the final interval: ...
0
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0answers
11 views

Assign attributes / categories to users based on their activity / likes

I have a very practical classification problem for which I need some help. I have a database of users along with their activity / likes for a number of car models. I also have the category each of ...
1
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1answer
38 views

Standard error bars overlap but significance - estimated marginal means versus observed means

I'm running a Mixed effects model ANOVA with two fixed factors (condition, repetition) and one random factor (subject). Subsequently, a Tukey multiple comparisons test is performed. Now I'd like to ...
2
votes
1answer
64 views

First order statistics (min) of n non-identical but independent normal variates [duplicate]

While I have seen papers and posts about mean and variance of n i.i.d normal random variables, I am looking for the first order statistics of $n$ (specifically $11$) normal, non-identical (different ...
0
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0answers
80 views

Finding the value of the pressure to maximize mean

The peel strength ($Y$) of photo resist in the lamination process of PCBs depends on the pressure ($x$) and temperature ($z$) by the relation: $$Y = 50 + 5x + 10z + (20xz)-(.01(x^2)\cdot (z^2))$$ ...
3
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2answers
229 views

Outliers and the mean

I would like to know what the following example is called in mathematics: In a gymnastics competition the judges scored a competitor as 10, 8, 3, 7, 7, 9, and 8. I recall that the ending score was ...
2
votes
1answer
36 views

How to measure if a mean is stable

Background I am a physics major, however I am currently interning at a psychiatry/neuro-imaging laboratory. The primary area of research in my lab is diffusion tensor imaging (DTI). A lot of the ...
2
votes
1answer
31 views

Run Many Small or a Few Big Simulations to Estimate the Mean?

I was just running some simulations on tossing a coin given certain conditions, to test out some ideas I had. I was trying to find the ratio $\frac{\mathtt{successful\ tosses}}{\mathtt{total\ ...
1
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1answer
25 views

Assuming the true mean

I've collected fluorescence data from some bacterial cells. Each cell has a gene in it which can be induced to fluoresce. However, even without being induced, the gene will still fluoresce a little. ...
1
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0answers
42 views

Mean imputation/estimation of missing data

Could someone please refer me to papers that have imputed the mean to missing values of a continuous variable? (i.e. papers that have used mean imputation) I have imputed my missing IMD values using ...
2
votes
2answers
96 views

How do I calculate confidence intervals for a non-normal distribution?

I have 383 samples that have heavy bias for some common values, how would I calculate the 95% CI for the mean? I the CI that I calculated seem way off, which I assume is because my data does not look ...
0
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0answers
9 views

Standard error for expected value [duplicate]

I have a computer simulation from which I get a sample of values of some microscopic quantity $X$, i.e. $\{ x_1,\ldots,x_N \}$. I'm interested in estimating the expected value of $X$, i.e. $E[ ...
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0answers
20 views

Mean squared error / Max error squared

I'm use this metric for variation that is similar to CV, but it is guaranteed to be on a 0 to 2 scale for positive numbers, where 2 is "all over the place" and 0 is "perfectly even". Since its ...
5
votes
1answer
72 views

Why are Winsorized random variables independent?

While studying trimmed mean I understood that if I have some random variables $X_1, X_2, .., X_n$ by ordering them and trimming, the variables are no longer independent. However it is said that "by ...
0
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1answer
77 views

High Standard Deviation for Leave one out cross-validation?

I am using the leave one out cross-validation technique to evaluate my model. If the prediction on the test sample is right the output is 1 otherwise 0. So I have a array of N samples with 0's and 1's ...
2
votes
1answer
51 views

Standard Deviation After Subtracting One Mean From Another

I've got two sets of data from some fluorescent cells. The first set is when the cells don't have their fluorescence switched on, but they are still faintly glowing. The second set is when they do ...
4
votes
3answers
122 views

Estimating the ratio of cell means in ANOVA under lognormal assumption

I am conducting a two-sample test (1-way ANOVA with 2 treatments), and the goal is to estimate the ratio of cell means assuming that the data are lognormal. A simple approach is to log the response ...
1
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1answer
36 views

How to Test if the Difference between Two Means from Different Samples are Significant?

here are distributions of four samples: and the following is the table of data: I would like to test: (1) if the difference between means of "Give" and "Work-Give" samples is significant; and (2) ...
0
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1answer
16 views

Given MTTF and Number of Items, how to calculate failing parts with Time?

I am wondering how to make use of MTTF Here is the situation, I am given an MTTF for an item type x and a certain demand for that item in the next 25 years, say 100 parts that will be in operation ...
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0answers
4 views

Contribution of residuals to the mean error

I have data for 1000 students' performance over 10 different tests on a scale of 0 -100 (a 1000 rows X 10 col matrix). I calculated the mean score and the associated std. deviation for each student. ...
2
votes
0answers
62 views

Average of predicted values with logistic regression

I have a large unbalanced dataset (the target has ~1500x more 0's than 1's) on which I train a logistic regression algorithm to predict the probability of success (Not a binary outcome but a real ...
3
votes
3answers
167 views

Should I use t-test on highly skewed and discrete data?

I have samples from a highly skewed dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want to compare their mean. For that, I'm using ...
7
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1answer
718 views

Should I use t-test on highly skewed data ? Scientific proof, please?

I have samples from a highly skewed (looking like an exponential distribution) dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want ...
5
votes
1answer
254 views

Name for the special estimate of the mean

During my masters studies, I heard about the following estimate of the mean: We take the minimal and the maximal value from sample and simply average them out. Does this estimate have any name? And ...
1
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0answers
28 views

Mean accuracy for sum of squares/variance

Formality says that when computing the sample variance or sum of squares one computes a sample mean with the sample data given. If for some reason I had access to a better estimate of the mean (from ...
3
votes
1answer
58 views

Do you need to report the standard error of the mean when the sample is the population?

The other day, my tutor told me that whenever a mean value is reported, the standard error of the mean must be reported alongside. But surely this isn't always the case? For example, let's say we ...
0
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0answers
23 views

Evaluating mean-squared error

Hello I am running a Regression Tree experiment. I am new to Regression Trees, and I am using Mean Squared error to test my tree. I am confused because I am getting a large Mean Squared Error but I ...
1
vote
1answer
60 views

How to calculate the variance for mean of means?

I have been reading up on how to calculate variance for different situations and the following has me confused….. If I take a number of samples (e.g. choose 5 kids in a class and ask them how many ...
1
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0answers
17 views

How can I calculate a confidence interval for true mean of one set being higher than another, based on samples from each?

I have two sets A and B each containing N elements and want to show that the true mean of A is less than that of B with certain degree of confidence. (Specifically, the sets represents items of "yes" ...
2
votes
1answer
50 views

What is $\bar\mu_n$?

Am I right in thinking that it is the average of the sum of $n$ different populations means? Here it is used in the context that confused me. It's the Chebychev WLLN, apparently. "If $x_i, i = 1, ...
4
votes
3answers
92 views

Comparing the mean difference between data measured by different equipment, t-test suitable?

My problem is as follows: I have 2 measuring devices, both using different measuring techniques, each trying to quantify properties of objects passing their measurement area. The devices measure the ...
1
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0answers
35 views

Formula for “adjusted mean” - Is this correct?

I am working on a software project involving statistical analysis of myoelectrical signals (EMG). One client requested the calculation of "adjusted average" for a given signal interval. His ...
2
votes
1answer
32 views

Comparison of two means

Which test should I use, if I want to compare the mean of the whole sample with the mean of the fraction of the sample? So for example the mean of the whole classroom taking the test and the mean of ...
0
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1answer
33 views

Does the standard error assume the mean is the centre of the distribution?

In statistics we can calculate a mean of a sample and the standard error of the mean. Let's say the mean of a sample is 2 and the standard error 1.5. If we repeatedly sampled from this population, it ...
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0answers
33 views

Different means with barchart and descriptives in SPSS

I have a dataset (in SPSS 22) with different measurements of children, with the children in rows and with the measurements as variables in the columns. For example, the activity levels of the children ...
2
votes
0answers
43 views

Averaging z scores when doing a “group by”

I have a dataset where each row is an hourly measurement of certain fields (columns). For each column I then add another column that is its respective z score relative to the entire population. If I ...
5
votes
2answers
192 views

Drawing numbered balls from an urn

PROBLEM There is an urn with a set of balls where each ball is labeled with a different integer. The numbers on the balls are known and are not a range of integers. For example the set of balls could ...
1
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1answer
22 views

Using more measurements of lower quality or just the one with the best quality?

I am currently trying to analyze some pupillometry data. The device I use gives me X and Y measurements of the pupil area (from which I compute the total area via $A = \pi \times ...
3
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0answers
112 views

Better estimator of expected sum than mean

I am trying to find the optimal estimator for the maximal expected $\Sigma X_i$ where $X_i$ is sampled from an unknown distribution which is chosen to be maximal. To clarify and simplify, there are ...