eCPM management

Much I have read google guidelines on eCPM, I do not manage to understand it.

Specifically these are the aspects I don´t quite understand.

. why pages with same targeted keywords have different eCPM?.
. Is eCPM connected with CTR?. The better the CTR the higher the eCPM.
. Is there any way to keep control of your eCPM?
. A page´s google ranking, has it to do with the page´s eCPM?
. Why does it always gradually drop as the day passes along?
. is the google keyword tool appropiate for finding adsense good keywords?
. What is the differece with with CPM?


Basically my interest goes for the 4 first questions,

thank you for your time,

 

There is no control to your ecpm
Your pages google ranking on which keyword basis depends on ecpm
yes google keyword tool appropriate for finding adsense good keywords