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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

What is a probability of drawing a club and a 7?

drawing a club

total club =13

P(Club)= 13/52

drawing a 7

total 7 = 4

P(7) = 4/52

P(a club and a 7) = P(Club) + P(7) as events are mutualy exculisve

P(a club and a 7) = 13/52+4/52

P(a club and a 7) = 17/52

If you roll a fair die what is the theoretical probability of getting a 5?

Since there are 6 numbers on a die (1-6), then the probability of rolling a 5 would be 1 out of 6.

What is the probability of having a girl versus having a boy?

The probability of having a girl versus a boy is 1/2 because there is two things you have a chance of getting and you can only get one or the other.

If the number of customers follows a Poisson distribution with a rate of 5.6 per minute what is the distribution of the time it will take for the next two customers to arrive?

Average number of arriving customers in 4 minute interval is 2.8 and poison distributed what is the probability that exactly six customer will arrive in a 4 minute interval?

If you roll two fair dice what is the probability you will roll a sum of nine?

You can roll (3,6), (4,5), (5,4), or (6,3). So that's four possibilities out of 36. So 4/36 or 1/9.

While flipping a coin 100 times John gets 44 heads and 56 tails Enter the theoretical probability of getting a tail while flipping a perfectly balanced coin?

Every time you flip a coin it has a 50% chance of heads and a 50% chance of tails. Flipping a coin multiple times does not change that. Therefore the answer is 50%

What is the probability of rolling the same number when three number cubes are rolled?

The first roll doesn't matter for probability, it just sets the number to be rolled by the other two. So:

P(rolling the same number three times) = P(rolling a particular number)2 = (1/6)2 = 1/36

What is the definititon of a discrete random variable?

The discrete random variable almost always arises in connection with counting.

Addition rule for probability of events A and B?

If they're disjoint events:

P(A and B) = P(A) + P(B)

Generally:

P(A and B) = P(A) + P(B) - P(A|B)

Mean and standard deviation of probability density function?

Suppose the probability density function is f(x), defined over a domain D

Then the mean is E(X) = x*f(x) integrated with respect to x over D.

Calculate E(X2) = x2*f(x) integrated with respect to x over D.

Then Variance(X) = E(X2) - [E(X)]2

and Standard Deviation = sqrt(Variance).

If you flip a coin 5 times what is the probability that the coin will land on heads all five times?

The probability that the coin lands on the heads ones: 1/2

Two times (1/2)^2 = 1/4

Five times (1/2)^5 = 1/32 (so 1 in 32 attempts)

n times (1/2)^n

What is an event that occurs because of a preceding event?

A dependent event. Or rather, a dependent event is one whose probability of occurrence is affected by previous events. For instance, drawing a card from a deck is affected by previous draws, if there's no replacement.

Sample space of tossing a coin 6 times?

{hhhhhh, hhhhht, hhhhth, hhhhtt, hhhthh, hhhtht, hhhtth, hhhttt, hhthhh, hhthht, hhthth, hhthtt, hhtthh, hhttht, hhttth, hhtttt, hthhhh, hthhht, hthhth, hthhtt, hththh, hththt, hthtth, hthttt, htthhh, htthht, htthth, htthtt, httthh, htttht, htttth, httttt, thhhhh, thhhht, thhhth, thhhtt, thhthh, thhtht, thhtth, thhttt, ththhh, ththht, ththth, ththtt, thtthh, thttht, thttth, thtttt, tthhhh, tthhht, tthhth, tthhtt, tththh, tththt, tthtth, tthttt, ttthhh, ttthht, ttthth, ttthtt, tttthh, ttttht, ttttth, tttttt}

Edit: It removed all my capitalization, but everything should be capitalized.

A sack contains red and blue marbles The ratio of red marbles to blue marbles is 43 If there are 16 red marbles in the sack how many blue marbles are in the sack?

This problem doesn't lead to a whole number solution. Are you sure you copied it correctly? Maybe you meant the ratio is 4 to 3. In that case:

red/blue = 4/3

blue/red = 3/4

blue = (3 * red) / 4 = (3 * 16) / 4 = 12 blue marbles