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

Slaking
Slaking
Base
stats
Stats Effort Possible genes (IVs)
Level
HP 150
406–436
3
Attack 160
321–352
8
Defense 100
203–233
14
Special Attack 95
193–223
12
Special Defense 65
133–164
27
Speed 100
203–233
17

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

This Slaking's Hidden Power inflicts Water damage, with 53 power.

And for your copy/pasting pleasure:

3 HP; 8/14 Physical; 12/27 Special; 17 Speed

or start over