Math Is Fun Forum

tinbird

Member

Registered: 2010-11-02

Posts: 11

Probability

Let X denote the reaction time, in seconds, to a certain stimulant and Y denote the temperature (oF) at which a certain reaction starts to take place. Suppose that two random variables X and Y have the joint density,

fXY(x,y)={4xy, 0≤ x ≤1, 0≤y≤1
                 0, elsewhere

Find
a.    P(0 ≤X≤½ and ¼ ≤Y≤½ );
b.    P(X< Y)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Probability

Hi tinbird;

I have answered a similar question over here:

http://www.mathisfunforum.com/viewtopic … 35#p155135

Please read this:

http://www.mathisfunforum.com/viewtopic.php?id=14654

I still do not know what you are having a problem with, Please show some of your own work, your ideas.
You are studying from an advanced engineering text, one of the best. You must be in an advanced class.
So you must know something about this. I answered your other questions hoping that it would get you going.

Now come on, work with me a little bit. What do your notes say? Let us start there.
I am not terribly interested in answering Kreyszigs book (homework) problems but I will help with your problems in math!

Do you understand that the area under some curve represents the probabilites that you want. That is what essentially statistics boils down to.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

tinbird

Member

Registered: 2010-11-02

Posts: 11

Re: Probability

Well i am extremely thankful for the help you and other Bob has provided. Actually the problem is with concepts and applying correct formulas. i am first time studing statistics and probability. Now the instructor is not clear himself in class and creates alot of confusions. even combinations and permutations your website has elaborated in a very easy manner and he made it  very difficult.

I usually understand the concept but when it comes to applying formulas i get confuse. Yes i have solved the question as you mentioned in above link and since i was unable to delete this post so couldnot do it after you replied same in other question.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Probability

Hi tinbird;

I am not following you. Are you saying you can do this problem?

Let X denote the reaction time, in seconds, to a certain stimulant and Y denote the temperature (oF) at which a certain reaction starts to take place. Suppose that two random variables X and Y have the joint density,

fXY(x,y)={4xy, 0≤ x ≤1, 0≤y≤1
                 0, elsewhere

Find
a.    P(0 ≤X≤½ and ¼ ≤Y≤½ );
b.    P(X< Y)

You have me confused. You still are not showing any of your own work so I do not know where to start! Please follow what I am doing and answer the questions I ask. Look at part a)

a.    P(0 ≤X≤½ and ¼ ≤Y≤½ );

On page 1034 Kreyszigs book 9 th edition. In your book look for Continuous Two Dimensional Distributions. Formula #7

Can you now solve a? Please answer!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.