WHIRLWIND EXPLANATION: Pokémon have a fixed, permanent score from 0 to 31 for each stat that affects how good that stat can ever get.

This calculator will figure out that score (called a "gene" or, more obtusely, an "IV") for you, so you can discard the unworthy. It's more accurate for higher-level Pokémon, so it's helpful to go into a level 100 wifi battle with someone and check your Pokémon's stats from there.

Stat calculator

Tyranitar
Tyranitar 		Base
stats		 Stats Effort Possible genes (IVs)
Level
HP 100
307–337
31
Attack 134
270–301
31
Defense 110
222–253
31
Special Attack 95
193–223
31
Special Defense 100
203–233
31
Speed 61
125–156
31

Congratulations, you've narrowed your Pokémon's stats down exactly!

This Tyranitar's Hidden Power inflicts Dark damage, with 70 power.

And for your copy/pasting pleasure:

31 HP; 31/31 Physical; 31/31 Special; 31 Speed

or start over