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Probability Fact Profile
Probability Fact

@ProbFact

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145,057
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Media
420
Statuses
8,045

Daily tweets on probability from @JohnDCook .

Joined November 2009
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@ProbFact
Probability Fact
2 years
Putting probability to work
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@ProbFact
Probability Fact
2 years
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
2 months
No, there’s a 50-50 chance two people share SOME birthday, not a PARTICULAR birthday.
@ostensiblynil
unconquered haploglyph
3 months
if you're in a room with at least 23 people, there's a 50% chance that one of them shares your birthday
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@ProbFact
Probability Fact
2 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 years
Male heights have a normal distribution centered at 5' 10" with a standard deviation of 3 inches. The probability of an 8 foot tall man is on the order of 1 in 1,000,000,000,000,000,000. And yet there are men taller than 8'. The record is 8' 11".
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@ProbFact
Probability Fact
2 years
Var(X) = Var( E(X|Y) ) + E( Var(X|Y) )
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@ProbFact
Probability Fact
9 years
"Probability is the intersection of the most rigorous mathematics and the messiest of life." -- Nassim Taleb
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@ProbFact
Probability Fact
2 months
Probability distribution relationships
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@ProbFact
Probability Fact
2 years
Discrete probability is conceptually easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
10 months
Var(X) = Var( E(X|Y) ) + E( Var(X|Y) )
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@ProbFact
Probability Fact
1 year
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
10 months
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
6 years
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@ProbFact
Probability Fact
3 years
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@ProbFact
Probability Fact
18 days
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@ProbFact
Probability Fact
10 months
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
4 years
Conditional probability is subtle. All probability is conditional. Therefore all probability is subtle.
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@ProbFact
Probability Fact
5 years
Next in the review queue: Bayesian Probability for Babies
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@ProbFact
Probability Fact
3 months
Var(X) = E(X²) - E(X)²
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@ProbFact
Probability Fact
1 year
'There are only five probabilities the average human can handle: 99 percent, one percent, 100 percent, zero, and 50-50. That’s it.” — Richard Thaler
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@ProbFact
Probability Fact
4 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
5 months
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 months
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@ProbFact
Probability Fact
2 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
4 years
Random phenomena are not obligated to follow one of the few dozen distributions that humans have given names to.
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@ProbFact
Probability Fact
1 year
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
4 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 years
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
8 months
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
4 years
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
1 year
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
1 year
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 years
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
5 years
The probability that two random integers are relatively prime is 6/π^2.
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@ProbFact
Probability Fact
7 months
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
29 days
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
1 year
Discrete probability is conceptually easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
4 months
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
4 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 months
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
1 year
'Monte Carlo is an extremely bad method; it should only be used when all alternative methods are worse.' -- Alan Sokal
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@ProbFact
Probability Fact
9 months
Uncorrelated random variables are not necessarily independent.
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@ProbFact
Probability Fact
2 years
Uncorrelated random variables are not necessarily independent.
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@ProbFact
Probability Fact
4 years
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
4 years
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
5 months
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
4 years
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
7 months
Discrete probability is conceptually easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
4 months
Var(aX + bY) = a² Var(X) + b² Var(Y) + 2ab Cov(X, Y)
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@ProbFact
Probability Fact
4 years
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
8 years
If I flip a coin, look at the result, but don’t show you, its state is random for you but not for me. Probability describes knowledge.
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@ProbFact
Probability Fact
4 years
'Monte Carlo is an extremely bad method; it should only be used when all alternative methods are worse.' -- Alan Sokal
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@ProbFact
Probability Fact
4 years
Discrete probability is conceptually easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
4 years
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
3 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
4 years
'... the theory of probabilities is at bottom only common sense reduced to calculus.' -- Pierre-Simon Laplace
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@ProbFact
Probability Fact
1 year
A random variable is a measurable function on a probability space.
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@ProbFact
Probability Fact
1 year
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
5 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
6 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
5 months
Var(X) = Var( E(X|Y) ) + E( Var(X|Y) )
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@ProbFact
Probability Fact
6 years
One way to think of the Markov assumption: The future is independent of the past, given the present.
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@ProbFact
Probability Fact
3 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
4 years
Markov assumption: The future is independent of the past, given the present.
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@ProbFact
Probability Fact
4 years
If A makes B more likely, B makes A more likely. P(B | A) > P(B) => P(A | B) > P(A).
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@ProbFact
Probability Fact
5 years
Information is quantified in terms of surprise. If everything in a message is expected, then it contains no information, no matter how long it is. #informationtheory
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@ProbFact
Probability Fact
5 years
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
4 years
Bayes theorem is easy to prove, hard to understand.
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@ProbFact
Probability Fact
1 year
“It doesn’t matter that you’ve had 10 girls in a row. The chances that the next child is a boy are 50-50.” Not necessarily. 🧵
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@ProbFact
Probability Fact
3 years
Uncorrelated random variables are not necessarily independent.
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@ProbFact
Probability Fact
1 month
'There are only five probabilities the average human can handle: 99 percent, one percent, 100 percent, zero, and 50-50. That’s it.” — Richard Thaler
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@ProbFact
Probability Fact
3 years
If P(A | B) > P(A) then P(B | A) > P(B). If B makes A more likely then A makes B more likely.
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@ProbFact
Probability Fact
4 years
Var(X) = E(X^2) - E(X)^2
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@ProbFact
Probability Fact
3 years
Uncorrelated random variables are not necessarily independent.
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@ProbFact
Probability Fact
2 years
“There areonly five probabilities the average human can handle: 99 percent, one percent, 100 percent, zero, and 50-50. That’s it.” — Richard Thaler
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@ProbFact
Probability Fact
3 months
“A thing appears random only through the incompleteness of our knowledge.” -- Spinoza
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@ProbFact
Probability Fact
3 months
Uncorrelated random variables are not necessarily independent.
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@ProbFact
Probability Fact
2 years
Var(aX + bY) = a^2 Var(X) + b^2 Var(Y) + 2ab Cov(X, Y)
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@ProbFact
Probability Fact
4 years
Var(X) = Var( E(X|Y) ) + E( Var(X|Y) )
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@ProbFact
Probability Fact
1 year
'There are only five probabilities the average human can handle: 99 percent, one percent, 100 percent, zero, and 50-50. That’s it.” — Richard Thaler
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@ProbFact
Probability Fact
8 months
A normal random variable is within two standard deviations of its mean about 95% of the time.
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@ProbFact
Probability Fact
5 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
5 months
The standard deviations of independent random variables add like the sides of a right triangle.
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@ProbFact
Probability Fact
5 years
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
8 years
OH: "Not everything is Pareto distributed, but 80% of it is."
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@ProbFact
Probability Fact
6 years
Bayes theorem says the order in which you learn about two things doesn't matter. P(A) P(B | A) = P(B) P(A | B) You could first learn about A, and then learn about B given A, or you could first learn about B, then learn about A given B.
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@ProbFact
Probability Fact
2 years
The central limit theorem says that CDFs converge. The corresponding PDFs may not converge.
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@ProbFact
Probability Fact
5 years
Discrete probability is easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
6 years
E( E(X|Y) ) = E(X)
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@ProbFact
Probability Fact
2 months
Discrete probability is conceptually easier than continuous probability because counting is easier than measure theory.
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@ProbFact
Probability Fact
6 years
'Probabilistic' comes from Latin. 'Stochastic' comes from Greek.
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@ProbFact
Probability Fact
13 days
'Monte Carlo is an extremely bad method; it should only be used when all alternative methods are worse.' -- Alan Sokal
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@ProbFact
Probability Fact
10 months
What probabilists call 'characteristic functions' everyone else calls Fourier transforms.
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@ProbFact
Probability Fact
2 years
One way to think of the Markov assumption: The future is independent of the past, given the present.
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@ProbFact
Probability Fact
4 years
Var(aX + bY) = a^2 Var(X) + b^2 Var(Y) + 2ab Cov(X, Y)
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@ProbFact
Probability Fact
6 years
Var(X + Y) = Var(X) + Var(Y) + 2 Cov(X, Y)
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@ProbFact
Probability Fact
3 years
Var(X) = E(X^2) - E(X)^2
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@ProbFact
Probability Fact
2 years
It’s not very useful to say heights are not normally distributed. Nothing is exactly normally distributed. It’s more useful to say how well the normal model fits, by what criteria, and under what conditions.
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@ProbFact
Probability Fact
4 months
If X has mean μ and variance σ², then (X - μ)/σ has mean 0 and variance 1.
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@ProbFact
Probability Fact
4 years
One way to think of the Markov assumption: The future is independent of the past, given the present.
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@ProbFact
Probability Fact
2 years
Bayes theorem is easy to prove, hard to understand.
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