Stat Manipulation, a.k.a. the ev, iv, base stat guide. This is your classic introlevel tutorial to how to manipulate your stats through Individual Values(breeding), Effort Values(training), and Base Stats(per species). The goal of this guide is to introduce regular casual players to the whole concept of stat manipulation and to show them how it works so as to introduce them to the world of competitive battling. So, let's start out by putting everything into layman's terms. What exactly are we talking about anyway? What's all that crap on smogon about competitive battling or the "meta game?" Why does Serebii talk about game mechanics? What are Evs and Ivs? Why should we care anyway? Well all this stuff revolves around the idea of manipulating the stats of your pokemon. For instance, back prior to the release of ruby and sapphire stats were a lot simpler, there wasn't a lot of science to it. With the release of ruby and sapphire though things became much more complicated. Ruby and Sapphire allowed an unprecedented degree of customization, so to speak, to your pokemon, in the form of stat manipulation (a.k.a game mechanics). Stat manipulation does several things. First off it really allows for the development of a new metagame. People refer to competitive battling as, generally speaking, the metagame. Basically the metagame refers to strategy and tactics within the realm of pokemon battling. You might remember that the original "special" stat was broken up into special defense and special attack. This however was only the beginning. Stat manipulation incorporates, at it's broadest level:  a certain fixed number, in each stat, per species of pokemon(base stats).  a certain random number, in each stat, which is generated when a pokemon is either hatched or caught, and is on an individual pokemon basis(IVs).  a maximum value, across all 6 stats, available to every pokemon, on a per pokemon/individual pokemon basis(EVs). This perhaps describes elementally what base stats, IVs, and EVs refer to.
Base Stats: So, time for some examples. As previously mentioned, each pokemon species has a set value in each stat which corresponds to the base stat. Weezing for instance has the following a base stat of 65 in Hp, 90 in Attack, 120 in Defense, 85 in Special Attack, 70 in Special Defense, and 60 in speed. (you can find these values in most pokedexes online. Both smogon and serebii among others all have base stats for each pokemon included in their pokedex entries.) Furthermore, You'll also probably see in any pokedex entry a set of Min and Max values. These min and max values take both natures and Evs into consideration and represent the maximum a pokemon's stat can go and the minimum a pokemon's stat can go. So Weezing for instance can have a maximum (with the correct + nature) of 372 in defense. In any event base stats essentially represent exactly what they sound like. They are the original values for which all subsequent manipulations (per stat) are based upon. This becomes very important when selecting pokemon for your team and base stats are vitally important in developing and determining tiers and a pokemon's place in a specific tier. The reason why Tyranitar for instance is OU has everything to do with how widely used Tyranitar is in the metagame, and thus he's included in the "Over Used" tier. But the reason Tyranitar is OU is because of his fantastic base stats and his excellent movepool which makes use of those base stats. Now, as mentioned, stat manipulation has to deal with the factors which increase a pokemon's stats and take hopefully take advantage of a high base stat (such as Weezing's 120 in defense). Thus we arrive at IVs, or Individual Values.
Individual Values: Individual Values (IVs) are the true beginning of the metagame. It is through IVs that you have such wide discrepancies in power between two of the same species of pokemon (one pikachu at lv. 100 being much stronger than another pikachu at lv. 100). Of course EVs will also help to account for such a discrepancy; but without IVs, such a discrepancy would be much lower. An IV though refers to a single value, in each stat, which is randomly generated. The value is between 0 and 31. These values are on a per pokemon basis. Which means each pokemon that you catch will have a random number, between 0 and 31, in each stat. Of course since this value is generated automatically when you first obtain the pokemon it cannot be altered once caught, similar to base stats. But unlike base stats an IV can be bred for. Thus breeding's primary importance can be seen in attempting to obtain higher IVs. But IVs are determined when you obtain the egg from the daycareman, and not when you've hatched it. To breed for Ivs basically means that you'll need the parents to have a high value in whatever IV you're trying to breed for. Breeding for IVs though is not easy. Even if your mother and father both have a 31 IV in attack (for instance) there's still only a 50% chance of that 31 being passed down to the child. In fact, for HP there is only a 1 in 6 chance of a 31 IV being passed to the child and 1 in 3 chance of passing an IV in defense. In RS and FRLG though all stats have the same chance of being passed, it's only Emerald and the fourth generation where HP and Defense are different. (Thanks to SkyUppercut60 for that information.) Furthermore, this is where the nature comes in. As you are probably aware a nonneutral nature (like modest for instance) will yield a 10% increase in one stat and a 10% decrease in another. Thus having the correct nature is almost as vital, if not more, then having all your IVs and EVs correct. Which is why having the everstone and being given a higher chance of passing a certain nature is so useful, if not essential to the whole breeding schema. In any event, for you to successfully get a 31 IV in all 6 stats and get the correct nature is extremely unlikely. The odds against you are arguably greater then finding a shiny pokemon in the wild. In any event, to review quickly about IVs.  There is a 50% chance of passing an IV, that both parents have to the child. But only a 17% chance in HP and a 33% chance in Defense.  Natures will increase one stat by 10% and decrease another stat by 10%.  Each of the 6 stats has a separate value, between 0 and 31. This brings us to our third and final term to cover; EVs. Otherwise known as Effort Values.
Effort Values: Effort Values represent the only values thus far that we have covered that are changeable. It is through Effort values in fact that we find a high degree of customization and versatility within the metagame. You may have seen on Smogon, specifically in their strategy articles, several different options, per pokemon. Aggron for instance has both a SubPuncher and a Choice Band moveset. The whole reason that Smogon and other players are able to identify separate move sets for each pokemon is because EVs exist. Without EVs Aggron might well be restricted to just a single effective moveset in the metagame (so to speak, obviously you could "use" any moveset, it's just certain movesets have been identified as working well within the metagame; i.e. when battling competitively.). Basically EVs though are identified by 510 separate points (EVs). EVs are gained by battling pokemon, and help to determine your pokemon's stat increases upon leveling up (with the exclusion of rare candies which do not take EVs into account when leveling up your pokemon). 510 though represents the maximum number of EVs your pokemon can obtain. Each EV though can be put into a certain stat. Thus Blissey can have 252 Evs in Hp, 252 in Defense, etc. Though obviously they must add up to 510. 252 is the limit of EVs per stat. So in reality you could max out two stats to their maximum (with 252 EVs, a 31 IV, and the correct nature). Because of this cap in the number of EVs you can apply to anyone stat, it's very important to identify what stats will be assigned what number of EVs. For instance, will you do a 4 HP / 252 Atk / 252 Spe spread of EVs on Dragonite so as to maximize the value of his Dragon Dance move set? Or will you do a 64 Atk / 252 SpA / 192 Spe spread of EVs so as to utilize a Choice Specs move set. Whichever you choose (and this choice will apply with variation for every pokemon) the way you spread your EVs out amongst your 6 stats will determine much. In fact, in the metagame certain values are identified as being the necessary # of EVs you must put into a certain stat so as to effectively combat certain pokemon. For instance, if you give Dragonite a naughty or lonely nature and 184 EVs in speed you will be able to effectively outspeed pokemon with a base stat of 115 in speed. This is the strategy in the metagame which must be so carefully brought into consideration when planning your team. Being able to outperform pokemon of a certain (often high) base stat is often essential for a pokemon to be effectively employed in a competitive battle. Now then the next part of the discussion turns to specific methods for effectively "EV training" your pokemon. As was mentioned, pokemon obtain EVs by battling other pokemon. Basically what this means is that every single pokemon in the game, when defeated, is worth a certain number of EVs in a certain stat(s). For instance. Defeating an Empoleon in battle (regardless of level) will bequeath 3 EVs in special attack to the pokemon that defeated it. It is thus important to ensure that you not only maximize the number of EVs a pokemon will earn per battle but to also keep track of how many EVs each of your pokemon has obtained and in what stats they have obtained them. Increasing the EVs of your pokemon can be facilitated in a variety of ways, as follows(credit to Judgment for the following): Power Items: These items boost the number of EVs gained per battle with a pokemon in their respective stat. They can be obtained at the Battle Tower for 16 BP each.
Power Ankle: Boosts Speed EVs
Power Band: Boosts Special Defense Evs
Power Belt: Boosts Defense EVs
Power Bracer: Boosts Attack EVs
Power Lens: Boosts Special Attack EVs
Power Weight: Boosts HP EVs
Equation goes like this:
x + y = t
x = EV's from pokemon y = EVs boosted from Power Items (+4) t = Total EVs
Now with Pokerus we multiply the whole left side of the equation by 2 so...
2(x + y) = t
Now assume we have a pokemon that grants 2 points per battle...
2(2 + 4) = 12 Speeding up EV Training
Macho Brace  Lowers the speed of the holder, but doubles the amount of EVs you get from one battle. (example: If you fight a Starly for Speed EVs, you get 2 EVs instead of the normal 1 EV.
Pokerus  Doubles the amount of EVs you get from a battle.
Vitamins  Adds 10 EVs to a stat, but stops working if that stat already has 100 more EVs in it.
EXP. Share  Not only does the wearer gain half the experience from a battle, but it ALSO gains EVs. So, for example, if someone battles a Pidgey for one EV of Speed, the both the Pokemon that battled and the wearer of EXP. Share gain 1 EV in Speed EACH. (If, say, a Pidgeotto battles and a Gastly is wearing the EXP. Share, then both Pidgeotto and Gastly each get 1 EV; the amount of EVs gained is not split in half.)
Reducing EVs In Pokemon Emerald version, there are 6 berries that can reduce EVs. Each one reduces 10 EVs from their respective stat.
 Pomeg Berry  HP  Kelpsy Berry  Attack  Qualot Berry  Defense  Hondew Berry  Special Attack  Grepa Berry  Special Defense  Tamato Berry  Speed While there are many places to EV train, I personally like to get my EV training done in Emerald since I can use secret bases. Basically what I do is I get another game, fill it's team with 6 of the same pokemon with 3 evs in whatever stat I need it in, then I trade information and go battle at that secret base. If I slap the macho brace on my pokemon I'm EV training that means I'll get 36 EVs from that one base. Which makes it a lot simpler. In theory it might take less time to go find pokemon and battle them in the wild; but I find that the secret base method is much easier to keep track of. Some spots in Diamond and Pearl where you can EV train your pokemon are as follows(credit to MKDS for the following): HP: Shellos at Valley Windworks north of ignore the Buizel (+1 each) Gastrodons at Fuego Ironworks or Route 213 ignore Floatzel (+2 each) Gastrodons outside of Pal Park (+2 each) Gastrodons at Route 222 (+2 Each, and are common their)
Attack: Kricketune and Bidarel at route 212 (rainy route) (+2 each) Bibarels and Machop (2 EVs and 1 EV respectively) Route 208 Machokes and Snovers at Acuity Lakefront (2 Evs and 1 EV respectively)
Defense: Cave with Geodudes and Hippopotas off route 214 (+1 each) (Ruin Maniac's Cave) Onix and Gravelers on Iron Island in the second room ignore Golbats (+1 Onix) (+2 Gravelers) Geodudes and Onix in the first room (Oreburgh Mines) (+1 each)
Special Attack: Gastly at the Old Chateau in Eterna Forest (+1 each) (Haunters +2) (Gengars +3) Golducks surfing in the water at the Resort Area (+2 each)
Special Defense: Surfing any ocean/sea area for Tentacools (+1each)
Speed: Raticates and Fearows Northwest of the Fight Area (+2 each) Route 225 Zubats in a cave (+1 each) Golbats in Victory Road (in water, you only find Golbats) (+2 each) Sneasles in Acuity Lakefront (+1 Each)
