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## #126 2012-11-09 05:52:25

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

The expected value is 1/probability is it not?

The matrix when computed should be 13.7

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #127 2012-11-09 06:07:04

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

http://www.wolframalpha.com/input/?t=cr … 5%2F6))%5D

How is the expected value 1/probability?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #128 2012-11-09 06:17:13

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

You did not enter the problem correctly
Matrix Inverse( IdentityMatrix[6] -  {{0,1,0,0,0,0 }, {0,1/6,5/6,0,0,0} ,{ 0,0,1/3,2/3,0,0} ,{ 0,0,0,1/2,1/2,0} ,{ 0,0,0,0,2/3,1/3} , {0,0,0,0,0,5/6 }}).{{1},{1},{1},{1},{1},{1}} gives the right result.

If the probability is 1 / 6 of something happening then we expect it to happen once in 6 times.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #129 2012-11-09 06:27:35

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

My result is correct. I just didn't sum the first row.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #130 2012-11-09 06:42:45

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

When I entered yours it says the trace is 14.7. The trace is the sum of the diagonal elements. It may or may not be correct.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #131 2012-11-09 06:47:32

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

The trace and the sum of the first row are the same for that matrix.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #132 2012-11-09 07:09:10

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Yes, but are you sure that will always be the case?

This way spits the answer out in a form that is 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.

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## #133 2012-11-09 08:19:59

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

No, I sum the first row. WA is the one who thinks you need the trace.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #134 2012-11-09 08:30:46

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

For one thing he did not interpret the identitymatrisx command correctly. For another the inverse was not calculated...

I would do it the way I showed in post#128.

Taking a little break.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #135 2012-11-09 08:45:29

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

That is not the same result I am getting when I press the link.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #136 2012-11-09 09:19:46

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Supposing others get my result? Isn't my way more reliable, since we are both getting the same answer. Also, my syntax is much closer to the package's syntax.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #137 2012-11-09 09:59:40

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

You just had multiplication by the vector (1,1,1,1,1,1) and I did the multiplication by hand. It is the same method.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #138 2012-11-09 10:23:12

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

I am talking about the syntax of the commands.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #139 2012-11-10 11:07:21

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

New problems?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #140 2012-11-10 11:51:12

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

A deck of cards are dealt out in a circle. What is the expected number of pairs of adjacent cards which are both black?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #141 2012-11-10 11:57:08

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

A standard French deck?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #142 2012-11-10 12:31:46

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

It is a regular deck of playing cards.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #143 2012-11-10 12:39:58

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

Okay.

What do you get as the answer for decks of 4 and 6 cards (half of which are black)?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #144 2012-11-10 12:46:15

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

E(4 card deck) = 2 / 3

E(6 card deck) = 6 / 5

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #145 2012-11-10 12:58:07

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

And E(8)?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #146 2012-11-10 13:08:29

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

E(8 card deck) = 12 / 7

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #147 2012-11-18 12:29:44

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

I haven't been able to find a solution...

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #148 2012-11-18 12:31:49

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

Okay, I can give the answer if you want it.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #149 2012-11-18 12:33:15

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Expectation

I'd rather get a method than an answer, but either is okay...

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #150 2012-11-18 12:43:51

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,436

### Re: Expectation

Hi;

I'd rather get a method than an answer,

Hmmmm. You should already have the answer or darn close to one. Have you forgotten how we work?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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