# Tagged Questions

In Probability and Statistics, the standard deviation of a statistical population or data set is a measure of how much variation or dispersion exists from its average value. It is defined as the square root of the variance.

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### Standard Loss Function L(z)

z is the standard normal distribution F(z) is the probability normal distribution L(z) is the standard loss function i can find these values using below code in the excel z=NORMSINV(x) F(z)=NORMDIST(...
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### Finding the variance of a group data set

Okay, so this is what I have so far for the means of these numbers. At this point I've added so many numbers together that my calculations are getting messed up. I need to know how to find the ...
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### How do I find the variance for a group data set?

Okay, so this is what I have so far for the means of these numbers. At this point I've added so many numbers together that my calculations are getting messed up. I need to know how to find the ...
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### A jar contains seven red and three green beans.

Four beans are randomly withdrawn in succession with replacement, and the number of red beans, $X$, is observed. Determine $\mu$, $\sigma_2$, and $\sigma$ for the random variable $X$. I'm not ...
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### How do I find the variance for a range of numbers?

Basically, my homework is asking me to find the variance based on a frequency table. But the frequency table looks like this: Frequency Table: Salary Number of Employees 5,001–10,000 8 employees ...
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### How do I find the variance for a range of salaries?

For instance, if I am looking at a frequency table and it says that 6 employees make between 5k-10k, 5 employees make 12k-18k, and 3 employees make 20k-25k...how would I find the variance if the ...
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### Am I on the right track with this question on standard deviation?

The final exam scores listed below are from one section of MATH 200. How many scores were within one standard deviation of the mean? How many scores were within two standard deviations of the mean? ...
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### Question about checking normal distribution and analysing confidence intervals

I've got another question about normal distribution and its confidence intervals interpretation. Your explanation will respectively help me to better prepare for my examination. One of the social ...
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### Two questions about normal distribution and its calculation

dear community members, I got this question in my handbook for exam preparation. I was trying to calculate the output but I'm stuck with figuring out the correct value. The question is: According to ...
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### Was it really necessary to have the variance be calculated with $\Sigma (X-\mu)^2$? [duplicate]

From what I understand, in calculating $$\sigma^2 = \frac{\sum (X - \mu)^2}{N}$$ the only reason why the squaring is done is to make distance from mean always positive. So my question, why couldn't ...
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### OLS on big data

We regress $Y$ on categorical data $X_1,…,X_p$. This is a large data set (that's right, big data!) but many of the rows of the design matrix are duplicated. We can summarize the data by averaging $Y$ ...
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### Normal Distribution and Percentile Word Problem

The Graduate Record Examination (GRE) is a test required for admission to many U.S. graduate schools. Students’ scores on the quantitative portion of the GRE follow a normal distribution with mean ...
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### Aggregating standard deviation to a summary point

I have a range of data (server performance statistics) is formatted as follows, for each server: ...
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