Can anyone help me with these maths?

[Bovinious]

Okay, so does anyone (any statistics majors out there?) know how to find the probability of drawing an X of (1 or more) in a Y card hand. For example, say I play 10 lands, whats the probability of drawing at least 1 land in my opening 7, and how is it calculated? Im assuming the same method could easily be applied to say 11 lands, 6 cards hands etc, I just dont know that statistics to start. Anyone got some hard statistics to help me out?

[conboy31]

I think it can be found here:
http://www.kibble.net/magic/magic10.php

[Lukas Preuss]

There's a calculator on the internet that helps you with just that: http://www.adsciengineering.com/hpdcalc/

It's basically just applying the Hypergeometric Distribution. Look it up on Wikipedia if you're interested in how it works.

Edit: How to use the calculator:
For your opening question, you just have to enter 60 as "Size of Space" since that's the size of your deck. You then enter 10 as "number of desirables", which are the ten lands you want to be playing. You don't have to enter anything as "number of undesirables", because it is clear that in this case, your deck contains 50 non-land cards. You "Sample Size" is 7, the cards you draw for your opening hand.

You get the following table:
i formula P
0 - 0.258629234297510
1 - 0.411455600018767
2 - 0.246873360011260
3 - 0.071557495655437
4 - 0.010657499352937
5 - 0.000799312451470
6 - 0.000027187498349
7 - 0.000000310714266

These are the probabilities of a 0-land hand, a 1-land hand, etc. To get the probability for "at least one land", you just have to look at the 0-land hand and subtract this number from 1.
1 - 0.26 = 0.74

So, in this case, there is a 74% chance of drawing at least one land in your opening hand.

[xsockmonkeyx]

There's a calculator on the internet that helps you with just that: http://www.adsciengineering.com/hpdcalc/...

Thank you oh so very much for this link and explanation. I am forever in your debt.