Using the Binomial Distribution function in excel

Hi SHG,

I've gone over the excellent piece of code that you contributed a few times and think that there is a small anomoly but cannot figure out exactly where.

I set up a small tool to use the function and think that the percentage split for heads and tails is being amplified too much when you seperate them.

When they are split 50/50 the results look correct but any other weighting looks wrong when I've experimented. I'll give a few examples:

50/50 split and the goal is first to reach 5 successes (best of 9):

Chances of either side winning (50%/50%)

2-1 (57%/43%)
3-1 (67%/33%)
4-1 (80%/20%)
3-2 (50%/40%)
4-2 (75%/25%)
4-3 (67%/33%)

Like I said before these look to be bang on in terms of reflecting the chances of either side winning.

In a 60/40 split with the same goal however I get these results:

Chances of either side winning (88%/12%) ???

2-1 (85%/15%)
3-1 (88%/12%) ???
4-1 (92%/8%)
3-2 (81%/19%)
4-2 (88%/12%) ???
4-3 (79%/21%)

With a 60/40 split the tails (40% side) has to get to a score of 0-4 before it is considered more likely to win which surely cannot be correct.

Have I applied the piece of code that you made me wrong or is there a simple solution the problem? I have attached a copy of the spreadsheet that I was using on here (the cells using the formula are in D13 and D14)

Once again, thanks for all of your help up until now I really appreciate it.


Thanks

Gadam