- #1
icystrike
- 445
- 1
Homework Statement
Hi PF! I am studying from a book - A first course in probability by Sheldon Ross, and I have came across this section whereby the are trying to prove the upper bound (equations 4.1 and 4.3) and lower bound (equation 4.2) of the inclusion-exclusion principle from basic probability. The section has been attached below:
However, I have not clearly understood two parts that have been stated in the attachment. The two parts are stated below;
1) They have mentioned "fixing [itex] i [/itex] " twice in the book, and what do they mean by that? I don't see the need for me to fix any "variable".
2) How can they simply get [itex] P(U_{j<i} E_{i}E_{j}) \geq \sum_{j<i}P(E_{i}E_{j}) - \sum_{k<j<i} P(E_{i}E_{j}E_{i}E_{k})[/itex] from (4.2)? What are the considerations that have to be made? My concern is towards the [itex] P(E_{i}E_{j}E_{i}E_{k})[/itex] of the equation.
Thanks in advanced :)
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