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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.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#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.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#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.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#7 2012-10-21 10:51:38
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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.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#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.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.