Questions tagged [arithmetic]

For on-topic questions involving arithmetic. Try to include also a more statistical tag. For purely mathematical questions about arithmetic, please use math SE https://math.stackexchange.com/

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Linear regression to compare proportions in different groups...?

Days ago I asked this question (Comparing proportions inside groups...?) and someone told me to compute a linear regression over each frequency distribution and compare the average residuals to see ...
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proof of a relationship related to half-normal distribution [duplicate]

Would anyone be able to help solve this: $\dfrac{\mathbb E[|X-\mu|]}{\sqrt{\mathbb E[(X-\mu)^2]}}=\sqrt{\frac2\pi}$ for a normal distribution. Related to the mean of a half-normal distribution?
Farzad's user avatar
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relationship between arithmetic mean and standard deviation in a normal distribution [closed]

I know that Sa divided by Sq (arithmetic mean/standard deviation) on a standard normal distribution is equal to 2/(2pi)^0.5 or 0.7978 but need to have the mathematical solution. Can anyone help me ...
Farzad's user avatar
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Reinforcement learning with simple integer arithmetic actions

Motivated by an experimental investigation in pure mathematics, I am interested in the following type of reinforcement learning problems: The state is a collection of N integers, where there are no ...
Andrei Smolensky's user avatar
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In mathematics, what is coefficient if variable is not having any coefficient in percentage equation?

If I am having equation as X-14.8%X = 5.98, then what is coefficient of variable X? Is it 1% or 100%?
AKSHAY MOTE's user avatar
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1 answer
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How to compare the mean to the mean of mean values of dummy variables?

I am trying to validate the calculations of a mean value for a collection of binary variable values. The validation process is where I compare x to y where: x is the mean value of percentage of ...
Zeinab Elashidy's user avatar
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1 answer
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"Values not normally distributed, so were transformed to log10 values before" - how to read the results?

I have been researching a medical topic and stumbled upon a paper that is really useful for me but I am limited by my math/statistics knowledge. The paper reads as follows: the Gmax and Tlag ...
PuzzleDoc's user avatar
7 votes
2 answers
1k views

How to find median value for five given elements based on the max min and sum of the elements

this question occurred in my interview, How to find the median values using the min, max, and sum values of the given 5 elements? for eg if given 3 elements we can use sum - min - max a = [3,6,9] here ...
Shivam Baldha's user avatar
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Difference between the terms "Frequency" and "Abundance"

How does Abundance or Relative abundance (Chemistry) differs from statistical frequency? Or it is just another term for statistical frequency in context of chemistry? Update: here are some example ...
FrustratedBird's user avatar
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1 answer
62 views

could $e$ in exponential distribution be replaced with other value?

I'm currently learning exponential distribution in class, and i have this random thought on my mind. so, as we know, the probability density function of exponential distribution is $f_X(x)=\lambda e^{-...
cynews09's user avatar
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Central limit theorem proof for ($\bar{x}_n - \mu$)

It's probably very simple but I am stuck to prove the variance of the central limit theorem in this case $x_{1}, x_{2}, \ldots x_{n}$ random sample. $E\left(x_{i}\right)=\mu, \operatorname{Var}\left(...
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How to determine the total vaccinated citizens given the number of 1st and 2nd dose administered? [closed]

Currently, there are 80,918 first COVID-19 vaccine doses and 52,949 vaccines that have been administered in my city. I am interested in looking at the total citizens who are either fully vaccinated or ...
Aidre Cabrera's user avatar
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1 answer
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Correctly averaging grades when tests are over different points

Suppose in a school the grading system is from $60,$ and you've done $3$ tests, $1$ over $60,$ and the other two were smaller tests over $40$ and $20$ points respectively. I am trying to learn what ...
user929304's user avatar
1 vote
1 answer
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Probability from Chi-Squared distribution

If I have a random variable called $A$ and $A \sim \mathcal{N}(0,1)$, how can I get the value of $X$ if $P(X<5A^2<6.52)=0.5310$. It seems that the answer is $2.4109$, but I don't know how to ...
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Equality of the Covariance of Two Random Variables and the Expected Value of the Product of One and the Difference Between the Other and Its Mean

I am trying to understand the second equality in the attached image. Could you please help me by guiding me as to how I can prove this? Thanks!
Aditya Verma's user avatar
3 votes
1 answer
307 views

How can I normalize price history between -1 and 1 while keeping the ratio of price differences to each other the same?

I want to normalize a series of numbers to all be between -1 and 1, but I would like to do it in a way where the relative difference between price elements stays the same, if possible. Example list of ...
Renoldus's user avatar
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Deep Learning: Should I dot product (input, weight) or dot(weight, input)? Does it even matters?

I've been following through Neural Networks from Scratch and found that the author switches the order of dot(input, weight) from time to time. The calculation shows that the dot product gives ...
Matt's user avatar
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2 answers
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How to calculate $\Delta Y$ given $\Delta X$, a simple linear equation, and a correlation score?

Suppose I conduct a correlation and SLR analysis on a bivariate data set and obtain the following: $$r=.63$$ $$Y=2.1+5.6X$$ If I increase X by 300, how much will Y go up?
marksmile's user avatar
2 votes
2 answers
176 views

Expected value homework question

Im not sure why the expected value that I got is incorrect. The method that I did is: (0)(0.568)+(7)(0.101)+(11)(0.218)+(9)(0.113)
user312021's user avatar
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1 answer
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What mean should I use when few big values? [duplicate]

for a project I need to calculate several means, I then compare each of these means to a distribution under the null hypothesis H0. However sometimes some values (...
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1 answer
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Combine Two Numbers that Satisfies these Five(5) Conditions with R [closed]

I want two(2) numbers $\phi_{1}, \quad \phi_{2}$ such that the following five(5) conditions will be satisfied using R: $ \phi_{1} + \phi_{2} < 1 $ $ \phi_{1} - \...
Daniel James's user avatar
-1 votes
1 answer
87 views

Odds to probability transformation

The odds are defined as $\omega = \frac{\pi}{1-\pi}$, where $\pi$ is the probability of some event. How can it be shown that the back-transformations is given via $\pi = \frac{\omega}{1 + \omega}$?
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Equation for weighted mean of percentages [closed]

I am trying to get the equation for a weighted average of percentages to be normalized between 0 and 1. Am I doing it correctly? Thank you so much!
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How to scale data proportionality as to equal 100%

I am applying for a grant for the nonprofit I run, and I have some data they need for the grant. However, this data does not equal to 100% and I need to know how to scale the data up so that it is ...
Chancee Culp's user avatar
3 votes
1 answer
910 views

Modelling exchange rates: how to log transform percentage changes?

I'm trying to model an exchange rate to test for extreme values. However, I have percentage changes from day to day. Given some changes are negative, I can't take the logarithm. Any idea how I could ...
Jackson12's user avatar
4 votes
1 answer
9k views

How to calculate 'times likely' for a percentage and whole number data set?

I'm analyzing speech data for single people vs those in group. I have two types of datasets for which I want to calculate "times likely". ...
slicer's user avatar
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-1 votes
1 answer
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Finding the number of teams

I played in a online tournament of a game of some sorts, and I want to know how many teams they were. I have the following informations : The team who finished in first place were on the Top 0.001% ...
Shan9588's user avatar
3 votes
1 answer
844 views

Calculating variance of poisson distributed random variable

I am calculating variance of a Poisson distributed random variable with mean $\lambda$. I am doing it in the following way: $\mathbb{V}(X) = \mathbb{E}(X^2) - \lambda^2 \\ = \sum_{x\geq 0} \quad x^2\...
anotherone's user avatar
2 votes
1 answer
154 views

Beta distribution, finding $\alpha, \beta$

Here the expected value and the variance are given, and it's needed to find the values of $\alpha,\beta$. From the Beta distribution and the elicited prior information, we can write: $E(\theta)={\...
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Negative variance of linear combination of regression coefficients

I'm going crazy over this so I hope someone can help me.. First a presentation of my case: I have a complex multiple regression model with 4 predictors (some terms that don't concern this issue are ...
ConfusedPhD's user avatar
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1 answer
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Simple Z-Score question dealing with normal mean and standard deviation I keep getting incorrect

The question below is simple, however, I got the question wrong despite following a basic formula I have been using for a while now. Here's the question: For applicants who actually entered medical ...
Ghetto Lisa's user avatar
0 votes
1 answer
46 views

Significance of Difference in arithmetic means

We characterized two social group through utilizing a 4 point likert scale and arithmetic means for 32 questions separated in 4 groups and 4 subgroups as our professor advised, we look at the ...
Lorenzo C's user avatar
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0 answers
261 views

Output Size of Mixture Density Networks

I am working on a neural network in which the final output layer will be a Mixture Density Network (MDN), but am confused about the shape of the values that final layer should return. In the paper in ...
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Squaring floats between -1 and 1 reduces sum of squares, so why do it? [duplicate]

I have been learning basic statistical testing as it relates to agriculture and have become familiar with the common practice of summing squared raw deviation values, whether in something simple like ...
Dodge's user avatar
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1 answer
150 views

Question on finding the variance

]1 For part B, I previously had 2.07 which is incorrect but why?! I literally followed the formula and I encountered a similar problem on the internet that did the exact same thing I did done below: ...
Ghetto Lisa's user avatar
1 vote
1 answer
76 views

simply considering square root of Variance as Standard deviation

Consider the following simple linear regression equation: $$y_i=\beta_0+\beta_1 x_i+\epsilon_i,$$ where $\epsilon_i\sim N(0,\sigma^2)$. Suppose I have confidence interval of $\sigma$ which is (....
time's user avatar
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1 vote
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Isn't HM a better way of averaging k fold cross validation scores than AM?

When calculating fscore we use the harmonic mean of precision and recall since hm penalizes situations when either of the two metrics is low while the other is large unlike the arithmetic mean. So ...
Atif Hassan's user avatar
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1 answer
42 views

Person months to annual risk

if a study reports a risk of 4 cases per 1000 person months can that be converted into an annual risk per 100,000 people? if so, how? Thanks
MHuck's user avatar
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1 vote
1 answer
411 views

Negative Binomial Coefficients -nCk = (n+k-1)Ck

I am unable to understand that why $\binom{-n}{k} = \binom{n+k-1}{k}.$ Please help me in understanding this.
manish's user avatar
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Brain teaser: 2 men can catch 2 fish in 2 minutes, at this rate, how many men can catch 500 fish in 500 minutes? [closed]

I found this interview question off of Quora. I'm unfamiliar with rate-related questions when there are 3 dimensions (men, fish, time). My intuition is: 2 men can catch 2 fish in 2 minutes then if ...
Amazonian's user avatar
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0 votes
1 answer
55 views

Finding 'conditional probability'

Q-) The number of injury claims per month is modelled by a random variable N with: P(N=n)= 1/(n+1)(n+2),where n>=0 Determine the probability of at least 1 claim during a particular ...
Slowdown Sloth's user avatar
0 votes
1 answer
35 views

In Think Bayes book about Posterior mean

Page 24, Think Bayes by Allen B. Downey. Can you explain me how he compute mean by this code : ...
Puntawat Ponglertnapakorn's user avatar
2 votes
1 answer
36 views

Definition of nonarithmetic law

I came across the term nonarithmetic, but I don't now what that means. It is a condition for a Proposition of a Paper I am reading. There it is said: Assume that the law of $\ln A_0$ is nonarithmetic....
Myrkuls JayKay's user avatar
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1 answer
81 views

Help regarding calculating z statistic and p value

I am trying to solve a problem but couldn't see any way around it. So far, here is the progress $\mu_{pop} = 10 $ $\sigma_{pop} = \sqrt12$ $\mu_{sample} = 12$ $z = (\mu_{sample} - \mu_{pop})/(\...
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Simplification of the Normal Kernel

The kernel of the normal distribution is typically written as : $ p(\theta | \mu, \sigma^2) \propto \exp\Big(- \dfrac{(\theta-\mu)^2}{2\sigma^2} \Big)$ where the normalizing constant is: $C = \dfrac{1}...
Said Hassan's user avatar
2 votes
1 answer
583 views

Triangle inequality with random variables

Suppose $a$ and $b$ are real numbers (positive in my case), $X$ is a real-valued random variable and $F$ is a set of functions. Are the following true? $|a-b| \le E_X|a-X|+E_X|X-b|$ $|a-b| \le E_X [\...
axk's user avatar
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1 vote
1 answer
10k views

What is the underlying math needed to answer the following questions:

Some background: I was applying for an entry level business analyst position, and I was completely lost with some of these questions. These questions were from the practice test. I'm not sure how I ...
Nahuatl's user avatar
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1 vote
1 answer
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Converting annual to daily mortality rate

In one excel workbook I am working on right now, the annual mortality rate is given as 3.082% And the formula for calculating the daily mortality rate is 1-EXP(LN(1-[annual mortality rate]/365) Why ...
Aywfto's user avatar
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1 vote
1 answer
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Is it better to take a mean of means or a grand mean when relaying rate data?

I am working with a dataset that includes number of fish caught in a day, and number of hours spent fishing that day. The variable of interest (outside of general summary statistics) is the number of ...
MANOVAboard's user avatar
1 vote
0 answers
138 views

How does this manipulation of summation of exponents work?

I found this paper by Fischer and Igel (2012) (1). I am not able to get past this last step in their derivations (eqn 22, p24) where $h_i$ are values of $h$. Can anyone tell me how they reduced the ...
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