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#1 2012-10-21 09:51:29
- genericname
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Probability density question
Given a random variable X with probability density f(x) = x/8 for 0 ≤ x ≤ 4:
1) What is the probability that X is between 1 and 3?
2) Find the expected value of X
How do you find the expected value for these type of questions? In general to find the expected value you use (x*(p(x)), so does that mean you have to plug in numbers 0 to 4 and apply the same formula after? Also for number 1 I got 1/2 as an answer.
Last edited by genericname (2012-10-21 10:04:07)
#2 2012-10-21 10:07:58
- bobbym
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Re: Probability density question
Hi;
I am getting that for 1 also, for 2) I am getting 8 / 3.
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#3 2012-10-21 10:22:42
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Re: Probability density question
What is the formula for getting 8/3?
#4 2012-10-21 10:26:10
- bobbym
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Re: Probability density question
I did it this way:
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#5 2012-10-21 10:42:39
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Re: Probability density question
I'm not quite understanding it. The value of x = 0, 1, 2, 3, 4?
#6 2012-10-21 10:45:31
- bobbym
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Re: Probability density question
Nope, the value of x is those and everything in between them. This is a continuous function.
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#7 2012-10-21 10:51:38
- genericname
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Re: Probability density question
How does it come up to 8/3? (Sorry for the dumb questions)
#8 2012-10-21 10:59:42
- bobbym
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Re: Probability density question
Hi;
Did you see post #4? That is the formula. I just took the endpoints from the problem.
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#9 2012-10-21 11:13:31
- genericname
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Re: Probability density question
Ah, thank you. I was overthinking it.
#10 2012-10-21 11:15:59
- bobbym
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Re: Probability density question
Hi;
Or maybe I am underthinking it. Anyway, hope that helps a little.
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.