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

Exeggutor
Exeggutor 		Base
stats		 Stats Effort Stats Effort Possible genes (IVs)
Level Level
HP 95
297–327
31
Attack 95
193–223
31
Defense 85
173–203
30–31
Special Attack 125
252–283
31
Special Defense 75
153–184
11
Speed 55
113–144
31

Hmm, I need more information to figure out your Pokémon's genes exactly. Try raising it to level 100 and entering its new stats.
Remember: if your Pokémon battles at all, you'll need to track the effort it gains. Consider saving your game and using Rare Candy instead.

And for your copy/pasting pleasure:

31 HP; 31/30–31 Physical; 31/11 Special; 31 Speed

or start over