30% Scrolls-For better or worse?

I basically just know 40 30% scrolls didnt work. I never kept track of how many broke things though (On the other hand, my sister is 13/14 with 30's and once on Tespia, I got 8 straight 10's to work).

I realize that each scroll has a 30% chance of working and that they're all independent on each other but you'd think I'd be luckier than getting under 10% of my 30's to work. I mean, with those rates, i was better off using 10%'s...

Hopefully the law of averages hold up. With this many failures, Im bound to get a 21 atk bwg without having to glitch sooner or later! >_>

Hmm...
Where to start...
Before I tallied up all my scrollings, I used to think that my 70%'s only worked 40% of the time, broke 40% of the time, and only fail no break 20% of the time. After I tallied it up, I realized that the 70%s actually worked 77% of the time.
Here's my documented record:
10% ~ 5 pass, 4+ fail
30% ~ 60 pass, 23+ fail, 19+ fail
60% ~ 36 pass, 37+ fail
70% ~ 99 pass, 13+ fail, 16 break

The + means that I'm uncertain of the undocumented ones.

The law of averages can be used, because although all probabilities are independent, why not just say that since we most likely won't find an ilbi, we won't find it? People will hunt monsters because when counting the success rate, you multiply the failure rate together and subtract that from one. For example, the chance that you'll find an ilbi after 20,000 spiders (which is the droprate btw) is 1 - (1-0.00005)^20,000 which is a 63% chance after killing 20K spiders.
I hope I'm making sense.
Subtract the failure rate is what I mean.