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Probability

The probability of a certain event is a number expressing the likelihood that a specific event will occur, expressed as the ratio of the number of actual occurrences to the number of possible occurrences. In mathematics, it is a measure of how often an event will happen and is the basis of statistics.

14,643 Questions

When are directed numbers used?

directed numbers are used for counting, measuring, adding, subtracting, dividing and multiplying. hope this helps which it probably wont :)

About the history of gamma distribution?

According to the links, Karl Pearson was first to formally introduce the gamma distribution. However, the symbol gamma for the gamma function, as a part of calculus, originated far earlier, by Legrenge (1752 to 1853). The beta and gamma functions are related. Please review the related links, particularly the second one from Wikipedia.

A coin is tossed and then a dice is rolled Find the probability of getting a 5 on the dice given that the coin landed tails up?

1/6 because there are six sides to a dice and we already know the coin landed tails up so that takes that equation out of the picture. otherwise we would be left with figuring the probability of the coin and the dice, but since the question tells us that the coin landed tails up the answer will then be 1/6

If the probability of an event is 0.42 then what is the probability of its component?

I haven't heard of a component with regards to statistics. If, by chance, you are referring to the complement, it is the probability that the event does not occur. In this case, the complement would be 0.58.

Chances of rolling a 12 on a pair of dice?

The only way to get a 12 is to get two sixes. The chance of rolling a six is 1/6 and chance of rolling two sixes is 1/36 or about 2.78%

How many different arrangements of the letters of the word doodle are possible?

There are 180 different arrangements, you may punch in 6! to your calculator and get 720 and think this is right but you have to take into account that "d" and "o" and doubled, so, the arrangements will give you a different answer.

6*5*4*3*2*1/4= 180

180 arrangements. :)

If 5 cards are drawn from a deck of cards without replacement What is the Probability that at least One of the cards is a 3?

If five cards are drawn from a deck of cards without replacement, what is the probability that at least one of the cards is a heart?

A ten sided die probability of rolling a four on 3 consecutive rolls?

The answer is 1 in 1000.
Rolling a 4 on a ten sided die is a 1 in 10 shot.
Rolling threes 4's is 1/10 x 1/10 x 1/10 which equals 1/1000.

Out of a standard 52 card deck what is the probability of drawing a heart given that a red card was drawn first?

This is a conditional probability, given the card is red, what is the chance it is a heart. Since there are 2 red hearts, the probability if 1/2

What is the approximate probability that a die with six sides that are each equally likely to appear will require more than 140 rolls for the total of all rolls to exceed 400?

More than 140 rolls will be required if and only if the sum of the first 140 rolls does not exceed 400

Let S = X1 + X2 + ... + X140 where Xi is the number obtained in the ith rollNote E[X] = 7/2, Var[X] = 35/12
So E[S] = 140(7/2) = 490, Var[S] = 140(35/12) = 1225/3
By Central Limit Theorem, (with continuity correction)
Pr{S ≤ 400}
≈ Pr{Z < (400.5 - 490)/√(1225/3)}
≈ 4.731327 * 10^(-6)

Define conditional probability with an example?

there are 3 types of conditional probability:

1. the indicate: if antecedent happens, then evidence manifests itself

example -> when tossing a coin, if it lands on tails, then you win the game

2. the subjunctive: if antecedent would happen, then evidence would manifest itself

example -> when a coin was tossed, if it would have landed on tails, i would have won the game

it is recommended for optimal bayesian inferences that your a priori distribution is indicative. If not, you could be dealing with inproper, uninformative, or hyper priors, which make decision-making and posterior determination more complex, if even possible.

Posterior distributions could very well be subjunctive. Suppose i have won the game, i could have tossed tails, but i could also have tossed heads.

What was the motivation for introducing the Gamma distribution?

It can be thought of as a generalization of the Chi-square distribution. See the link to a related WikiAnswer question below.

How does one find the probability of A given B compliment?

P(A given B')=[P(A)-P(AnB)]/[1-P(B)].

In words: Probability of A given B compliment is equal to the Probability of A minus the Probability of A intersect B, divided by 1 minus the probability of B.

What does fair means in probability?

From a probability perspective fair means equal probability.

What is the probability that a person chosen at random was born on a Saturday or Sunday?

2:7

edit:

That makes the assumption that:

-birth isn't induced for various reasons - people tend to try for induced births more on weekends so that it doesn't interfere with the work week

-the ratio of people born on any given day of the week is 1:1:1:1:1:1:1