Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [statistics]

Mathematical statistics is the study of statistics from a mathematical standpoint, using probability theory and other branches of mathematics such as linear algebra and analysis.

Statistics is the science of the collection, organization, and interpretation of data. It deals with many aspects of data, which includes the planning of data collection in terms of the design of surveys and experiments. (From Wikipedia)

More specifically, mathematical statistics is the study of statistics from a mathematical standpoint, using probability theory as well as other branches of mathematics such as linear algebra and mathematical analysis. (From Wikipedia)

For questions which are more generally about collecting and treating data, it is advised that you post your question on Cross Validated and DSSE.

37109 questions
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ELO ranking system: what's a good start rank?

I'm looking to implement an ELO ranking system. I've read the wikipedia articles and I'm confused about the start rank for players who enter the system at a later point. The common solution is to use a provisional ranking system but I'm curious if…
user257543
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concept of one-tailed hypothesis testing

When we assume that the null hypothesis is true in one-tailed test for mean, we assume that the population mean is equal that value indicated in the hypotheses. Why do we not assume some other value for the population mean also allowable under the…
TooOldToLearn
  • 459
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Necessary sample size for difference between means

Not looking for a solution, just wonder what formula to use (and why?): Given population A and population B, where: standard deviation(A) = standard deviation(B) = $100$ If I select equal sample size N from A and B, how big does the sample size need…
siegel
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Exponential distribution: Calculate $E(Y^a)$

For a Gamma distribution where $Y\sim \mathrm{Gamma}(\alpha, \beta)$ we have $$f(y)=\frac{y^{\alpha -1}e^{-y/\beta}}{\beta^{\alpha} \Gamma(\alpha)}$$ The question is, given that random variable $Y \sim \textrm{Expo}(\beta)$, derive a closed-form…
Sam Shen
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How do you find variance when not given probability?

A small farmer in a developing country grows cassava and groundnuts. The amount of cassava he grows per year is a random variable, X, with a mean of 500 pounds, and a variance of 625 (pounds-squared). The amount of groundnuts he grows per year is a…
Mary
  • 21
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Finding the mean of a Maxwell Distribution

Let the velocity of gas particles be modeled by the Maxwell distribution. The probability density function is $$ f(v) = 4\pi \cdot\left( \frac{m}{2\pi K T} \right) ^ {\frac{3}{2}}v^2\cdot e^{-v^2(m/[2KT])}$$ I found that the mean is $2a…
user12488
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Distribution of sample means for large number of samples

We are given normally distributed body weights with a mean of $195$ lbs. and a standard deviation of $24$ lbs. If an elevator in town has a maximum capacity of $20$ persons and a rated maximum weight of $4100$ lbs., what is the probability that the…
barb
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Multiplying/dividing mean and std dev of two different values

I'm working on predicting outcomes of games given statistics from the two teams involved. Two of the statistics I have are below: AGA (average goals against): The arithmetic mean of number of goals a team's opponent scored in each game. AOP (average…
wweavr
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find out how 'peaky' histogram is

I have a histogram made of number of detections made by an application: 9 instances of detecting 1, 1 instances of detecting 2 and so on. Say I have these histograms: first histogram: 9 1 1 second histogram: 9 2 0 I'd like to know the 'confidence'…
nonick
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Normal distribution problem - "6 times the standard deviation"

An old textbook says the range of data can be estimated as 6 times the standard deviation. If the data is normally distributed what percentage of the data is within the range? By 'range of data', does the question mean biggest - smallest? In that…
Jim
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What Field of Probability Deals With The Following

Say there is this hypothetical lottery. A ticket is USD 1.00; the chance of winning is 1 in 100,000,000,000,000,000; but the prize is more than USD 100,000,000,000,000,000. (For he sake of this argument, please ignore things such as “there is no…
blackened
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Correlation between sleep hours and brain activity

Say I am tracking my sleep for 1 week and these are the number of hours I sleep each night: (5, 6, 9, 4, 8, 9, 6) everyday that I track my sleep I am also taking a test that measures how well my brain is working these were my scores: (45, 23, 33,…
ahat91
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Exponential growth's power

If the number of Ebola cases are doubling every three weeks, how long before everyone in the world ($7$ billion population) will be infected? Sorry, I forgot to add that currently we have $3000$ cases. I'm just an English major but math layman. I…
Ed S.
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Help with financial modelling

We deal with "jobs" - a mini project involving multiple parties, resources and time constraints, etc. Jobs progresses through 4 well defined states from start to end; call them S1, S2, S3 and S4 where S1 is the start of the job and S4 is where we…
DJA
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Units of vaiance when variable is in %.

I have some confusion here. If some random variable is measured in some units, say $kg$ then clearly it's variance is measured in $kg^2$. But if the variable is dimensionless and measured say in $\%$ or base points in what unit the variance is…
Alexander Vigodner
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