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  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -




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Topic review (newest first)

2013-02-23 16:14:44

Oh! So inequality inside parenthesis in the probability arithmetic means sum of probabilities of all events which satisfy the inequality?
Well, it is kinda strange and unintuitive, but ok. I guess there is some logic in that and I would have to live with it...

But why not just write something like:

I think this would be more clear. Don't you think?

2013-02-22 14:47:54


Suppose you wanted to find

Hopefully it is obvious that
exactly when


Similarly, you have observed that
exactly when


What anonimnystefy is referring to in post #6 is that

is true and 0 if it is false.
This is also equal to

I hope this helps.

2013-02-22 07:09:58

Well? Does anyone have an answer?

2013-02-20 11:46:42

I am sorry, I do not understand your answer.
You said a=b=1? Where did 1 come from?
What exactly should I sum and why?
I am now even more confused...

2013-02-20 11:33:23

They are both 1. But if you multiply 1 by the probability that X is in fact 7 (or 8), and then sum over all values of X, you will get the probability.

2013-02-20 11:02:16

Ok, then lets take the k=2.

In that case we have two X which satisfy the inequality in parenthesis: 7 and 8.
Now what is the values of

Can you tell me the values for a and b?
What is the value of Pr(TRUE)???

2013-02-20 10:46:10

You need to find the probability that |X-3.2|>=18.3 . You can do that by summind the probabilities of all values of X for which that is hreater than 18.3 (which is in this case 0). And you probably know that 0<=0.01 .

2013-02-20 10:31:02

Yes, I read the definition, but it is not enough, I need a practical example.
Definition also says that it is true for all k>0.
So, if we have k=10:

Which X should I put here to see the truth of this inequality?

2013-02-20 09:45:48

That inequality means that the probability of the difference between X and mu being greater or equal to k*sigma is less than or equal to 1/k^2.

2013-02-20 09:43:20

I do not understand it.
Well, I kinda understand its meaning, but I am not sure how to read it or calculate it on a real numbers.

For example, if we have a pmf  table:

Now, how to calculate it for lets say k=10? or for k=100?
What goes for X in the inequality and what is the result of Pr() function?

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