For questions about estimation and how and when to estimate correctly

# Questions tagged [estimation]

1604 questions

**56**

votes

**12**answers

### What is the fastest/most efficient algorithm for estimating Euler's Constant $\gamma$?

What is the fastest algorithm for estimating Euler's Constant $\gamma \approx0.57721$?
Using the definition:
$$\lim_{n\to\infty} \sum_{x=1}^{n}\frac{1}{x}-\log n=\gamma$$
I finally get $2$ decimal places of accuracy when $n\geq180$. The third…

Argon

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### How to verify if a curve is exponential by eyeballing?

A plane curve is printed on a piece of paper with the directions of both axes specified. How can I (roughly) verify if the curve is of the form $y=a e^{bx}+c$ without fitting or doing any quantitative calculation?
For example, for linear curves, I…

arax

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**24**

votes

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### Prove that $e^\pi+\frac{1}{\pi} < \pi^e+1$

Prove that:
$$e^\pi+\frac{1}{\pi}< \pi^{e}+1$$
Using Wolfram Alpha $\pi e^{\pi}+1 \approx 73.698\ldots$ and $\pi(\pi^{e}+1) \approx 73.699\ldots$
Can this inequality be proven without brute-force estimations (anything of the sort $e\approx…

LHF

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votes

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### Mental estimate for tangent of an angle (from $0$ to $90$ degrees)

Does anyone know of a way to estimate the tangent of an angle in their head? Accuracy is not critically important, but within $5%$ percent would probably be good, 10% may be acceptable.
I can estimate sines and cosines quite well, but I consider…

brianmearns

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**16**

votes

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### Approximating $100!$

I participated in an Estimathon (a speed contest of Fermi problems) not long ago. It works as follows. Contestants are given questions and they must give a closed range $[a,b]$ which should contain the correct answer. The scoring guidelines are such…

Ahaan S. Rungta

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**13**

votes

**2**answers

### Probability vs Confidence

My notes on confidence give this question:
An investigator is interested in the amount of time internet users spend watching TV a week. He assumes $\sigma = 3.5$ hours and samples $n=50$ users and takes the sample mean to estimate the population…

hongsy

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**12**

votes

**1**answer

### Proving an integral is finite

I have the following integral:
$$\displaystyle \int_{\mathbb{R}^2} \left( \int_{\mathbb{R}^2} \frac{J_{1}(|\alpha|)J_{1}(|k- \alpha|)}{|\alpha||k-\alpha|} \ \mathrm{d}\alpha \right)^2 \ \mathrm{d}k,$$
where both $\alpha$ and $k$ are vectors in…

user363087

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votes

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### Is there a lower-bound version of the triangle inequality for more than two terms?

The triangle inequality $|x+y|\leq|x|+|y|$ can be generalized by induction to $$|x_1+\ldots+ x_n|\leq|x_1|+\ldots+|x_n|.$$
Can we generalize the version $|x+y|\geq||x|-|y||$ to $n$ terms too? I need to estimate an expression of the form $|x+y+z|$…

Bartek

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**10**

votes

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### How to know when to use t-value or z-value?

I'm doing 2 statistics exercises:
The 1st: An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30
bulbs has an average life of 780…

L.I.B L.I.B

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votes

**2**answers

### Approximate the second largest eigenvalue (and corresponding eigenvector) given the largest

Given a real-valued matrix $A$, one can obtain its largest eigenvalue $\lambda_1$ plus the corresponding eigenvector $v_1$ by choosing a random vector $r$ and repeatedly multiplying it by $A$ (and rescaling) until convergence.
Once we have the…

mitchus

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**9**

votes

**4**answers

### Why does finding the $x$ that maximizes $\ln(f(x))$ is the same as finding the $x$ that maximizes $f(x)$?

I'm reading about maximum likelihood here.
In the last paragraph of the first page, it says:
Why does the value of $p$ that maximizes $\log L(p;3)$ is the same $p$ that maximizes $L(p;3)$. The fact that it mentions that log is an increasing…

mauna

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### Estimating the sum $\sum_{k=2}^{\infty} \frac{1}{k \ln^2(k)}$

By integral test, it is easy to see that
$$\sum_{k=2}^{\infty} \frac{1}{k \ln^2(k)}$$
converges. [Here $\ln(x)$ denotes the natural logarithm, and $\ln^2(x)$ stands for $(\ln(x))^2$]
I am interested in proving the following inequality (preferrably…

Prism

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**9**

votes

**1**answer

### Estimates for the normal approximation of the binomial distribution

I'm interested in estimates of the normal approximation for binomial distributions, i.e. in estimates of
$$\sup_{x\in\mathbb R}\left|P\left(\frac{B(p,n)-np}{\sqrt{npq}} \le x\right) - \Phi(x)\right|$$
From the Berry-Essen theorem I can…

Stephan Kulla

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**8**

votes

**2**answers

### Modern formula for calculating Riemann Zeta Function

Possible Duplicate:
How to evaluate Riemann Zeta function
I have an amateur interest in the Zeta Function. I have read Edward's book on the topic, which is perhaps a little dated. I would like to know any modern methods for computing estimates…

JJG

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votes

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### A calculation that goes awfully wrong if we let $\pi=22/7$

Me and one of my friends had an argument and he said that using $22/7$ as value of $\pi$ is sufficient for any calculation. Can we always take it $22/7$, or is there some example of some calculation in which if we use $\pi=22/7$, some noticeable…

Bhaskar Vashishth

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