Probability Fact
@ProbFact
Followers
147K
Following
68
Media
476
Statuses
9K
Daily tweets on probability from @JohnDCook.
Joined November 2009
Probabilities of earthquakes and hurricanes https://t.co/zXvNAK0ehG // rocks have memory but air does not
1
0
12
A doubly stochastic matrix (i.e. non-negative entries, rows and columns sum to 1) is a convex combination of permutation matrices.
0
4
52
The so-called 'Mexican hat' wavelet is the second derivative of a Gaussian density.
2
3
34
Bloom filters are an efficient way to test whether an element is probably in a set. There is some chance of a false positive, but no chance of a false negative.
0
0
24
'... what is in itself the more certain may seem to us the less certain on account of the weakness of our intelligence.' -- Thomas Aquinas
0
0
12
If X ~ chisq(m) and Y ~ chisq(n) are independent then X/(X+Y) ~ beta(m/2, n/2)
1
0
18
A variation on Rock, Paper, Scissors
johndcook.com
Imagine a game of Rock, Paper, Scissors in which one player must choose each option the same number of times. How much of a disadvantage is this?
0
1
16
'All possible 'definitions' of probability fall short of the actual practice.' -- William Feller
2
9
37
How likely is a random variable to be far from its center?
johndcook.com
Chebyshev's inequality bounds the probability of a random variable being far from its center. You can get sharper bounds with slightly stronger assumptions.
0
2
27
On average, how many rolls of an n-sided die would it take before the sum of your rolls is at least n? https://t.co/Is6AsbSOpy
6
10
82
The Landau distribution is stable, i.e. a linear combination of Landau rvs has a Landua distribution.
en.wikipedia.org
1
2
19
Probabilities of data loss and data unavailability with replication and erasure coding https://t.co/aYSY0iffJ1 [pdf]
hitachihyoron.com
0
0
4