Math Is Fun Forum

suhana

Member

Registered: 2011-02-25

Posts: 31

last question cumulative disribution function

i'm hope any person tech me how answer this question ..becouse i'm try this morning and right now still do not have answer..i'm, stress about subject probability & statistics becouse I do not understand what he taught previously from my Lecturer..

thank all...

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: last question cumulative disribution function

Hi suhana,

Can you tell us how you have approached this problem? There's nothing difficult, all you need to know is simple definition of c.m.f, p.d.f etc.
Don't rely on lecturers, I rarely listened any.

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

c.m.f, p.d.f ?
file pdf?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: last question cumulative disribution function

Loosely the CMF or CDF is the area under the curve. The PDF is the curve itself. A .pdf file is a portable document file, it has nothing to do with statistics.

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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.

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

:touched can u explain i dont understand
did you answer the question or not?

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: last question cumulative disribution function

Hi suhana,

You would have known if you read the definition. Just once, read from a book or website. How can we help if you are not putting forth your effort?

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

okey..

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: last question cumulative disribution function

c.m.f, p.d.f ?
file pdf?

You wrote that, so I gave you some definitions that are very easy to understand.

---

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.

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

bobbym

it's okey..never mind, thanks alot..

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: last question cumulative disribution function

Hi suhana,

Here is a link to a file which consists of some problems similar to what you have asked:
http://www2.isye.gatech.edu/~rserfozo/courses/isye2027/NotesChapters1--3.pdf

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

can not be helping, and do not understand :(

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: last question cumulative disribution function

hi suhana

How did the wedding go?

Here's an introduction to pdf s and cdf s. 

I call  pdf a "probability density function" but other people say it stands for "probability distribution function".

It's the same thing mathematically whatever it's called.

cdf is "cumulative density (distribution) function"

The table at the bottom shows the probabilities when you throw a die.  Only six scores are possible.

But what do we do if any number in a range is possible, including decimals?

The pdf is  mathematical way of saying what the probabilities are.

The second picture below shows a graph for a possible pdf.

Any value between 0 and 10 is possible. 

The average value is 5.

Values near to 5 are more likely than values a long way from 5.

I made this graph using the program Excel with this formula:

I just made it up.  I wanted that shape and I wanted the area under the graph from 0 to 10 to add up to 1.

That's important because the area under any pdf must be 1. 

What that means is that the probabliity of having a value between 0 and 10 is 1.  No values outside this range are possible!

Furthermore, you can get the probability of the number being in any range by finding the appropriate area.

For example, the probability of x being between 2 and 4 is the area shaded blue on the diagram.

The area from 0 to x, written as a function is the cumulative function.

I made that

So P(2<x<4) = 0.2578

Let me know if you have understood so far.

Bob

Last edited by Bob (2011-02-26 23:48:53)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

suhana

Member

Registered: 2011-02-25

Posts: 31

Re: last question cumulative disribution function

aii bob..
so far enough ...
i do not want to ask again for someone, who does not prefer me ask of you