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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 the probability of finding a matching animal cracker from the bag 10 elephants 10 monkeys 10 horses?

When you take one cracker out of that bag, eat it, and reach into the bag

for another one, the probability that the next animal will match the first one

is

9/29 = about 31% .

What do you do if you are running a comparison to historical data and your background standard deviation is zero?

A standard deviation of 0 implies all of the observations are equal. That is, there is no variation in the data.

Is 21 a factor of 182?

No. 21 is not a factor of 182. The prime factorization of 182 is 21 x 71 x 131.

What is the sample space that results from rolling a red and black six-sided dice?

R1B1, R1B2, R1B3, R1B4, R1B5, R1B6,

R2B1, R2B2, R2B3, R2B4, R2B5, R2B6,

R3B1, R3B2, R3B3, R3B4, R3B5, R3B6,

R4B1, R4B2, R4B3, R4B4, R4B5, R4B6,

R5B1, R5B2, R5B3, R5B4, R5B5, R5B6,

R6B1, R6B2, R6B3, R6B4, R6B5, R6B6.

In a jar with 17 blue marbles and 43 black marbles when I grab 7 of them how many will be blue?

The total marbles are 60, your mathematical expectation of getting a single blue marble in one try is therefore 17/60. If you grab 7 random marbles, the mathematical expectation is 7 times 17/60. This is the expectation, in an actual experiment you will get more or less than that, but it should be fairly close to the calculated value. (Note that the mathematical expectation in this case isn't even an integer.)

Can you compute for mean absolute deviation with only 2 numbers?

Yes, it is 0.5*abs(a-b), where "abs" represents the absolute function: that is, a-b or b-a, whichever is greater.

How many ways are there of selecting a black card in a deck?

There are 26 different ways of selecting a black card from a standard deck of 52 cards.

How does one calculate factorials in probability on a TI 83 84 calculator?

Example: Calculate 6 factorial...

On the home screen [Clear]

Press [6] [Math] and the left arrow key - this selects the PRB menu

Press [4] for !

Press [Enter]

The answer, 720, is displayed.

What is a random vector?

A vector may be thought of as a magnitude or size (such as speed) and a direction. So a moving car may be represented by a vector that gives the car's speed and direction.

If the magnitude and direction of a vector are chosen from populations of values in some way that makes them unpredictable-or random in other words-then that vector can be said to be random.

What is the probability in rolling a prime and odd number?

First Answer:

With one six-sided die, the odds are one in two (right). With two dice, the odds are five in twelve (this is wrong).

Second Answer:

Broken down the following can be seen:

Number, Is odd?, Prime composition, Is prime?

1, Yes, 1^1, Yes

2, No, 2^1, Yes

3, Yes, 3^1, Yes

4, No, 2^2, No

5, Yes, 5^1, Yes

6, No, 3^1*2^1, No

Full disclosure however, the arguments that 1 and 2 are prime numbers are... well, debated. We'll just presume they are to simplify things (the arguments are rather complex compared to such a simple question; honestly though, I'm of the camp that believes 1 and 2 are not prime numbers, which makes the answer 2/6 for a single die).

So, the numbers that are both prime and odd are 1, 3, and 5. Really on a six sided dice you're just asking if what the probability that a number rolled is ODD will be. If this were a 16-sided die, the answer would simply follow the same logic, but be of a slightly different in nature.

The probability an odd number would be rolled is 1/2 for a single die (3/6). The probability that only one odd number would be rolled between two die is 1/2 * 1/2 (1/4). The probability that an odd number would be rolled but the other would be even (or visa versa) is still 1/2 * 1/2 (or 1/4). The probability that both are odd, or both are even is... again, 1/2 * 1/2 (or, again, 1/4). Lastly (and to answer your question), the probability that an odd number occurred at all when rolling two dice is the inverse of the probability that an odd number did not occur, which is 1 - (1/2 * 1/2) or 3/4, or 75%. If you think about it all possible combinations have been represented here. Take any given probability conjecture such as the probability that the first is odd and the second is even, because both possibilities are independently 1/2, the complement is likewise 1/2 and it makes life very, very simple when computing this.

How many different ways can you arrange the letters of the word awesome?

The word awesome has 7 letters where the letter eisrepeatedtwice. So there are 7!/2! = 7*6*5*4*3 = 2520 different ways.