Intelligence: Intelligence also helps crimes. Not tested.
Endurance: Once rumored to increase stat gains in the gym. Testing does not confirm this however.
Raising your Working Stats:
There is only two ways to raise your working statistics. The first is having a job, There are many different types of jobs, all giving their own unique bonus’ which help out greatly no matter what level you are or how experienced you are. IF you are just starting out, and are looking to get your working stats up as fast as possible, then please visit our New Player Guide, this will tell you when to start which career, to benefit you the most.
The second way of gaining working stats is to start an education. These cost a lot and take a long time to finish, but sometimes it’s well worth it. Do the educations courses strategically, find out which job/job rank you want to get to and take the courses according to that.
Remember, battlestats increase exponentially. This means that the more of one stat that you have, the faster it increases when you train. Keep this in mind when deciding what stat combination you want to train. Often it means that concentrating on few stats is more effective.
Here is the formula for battle stat gains;
For Strength, Dexterity and Speed.= (0.0002*STATS)+(0.00212*HAPPY+(0.55))
Stat Gain Defence = (0.0002*STATS)+(0.00212*HAPPY+(0.25))
Loosely translated this means that the more stats you have, the more you gain. And the more you gain, the faster you gain more…
Also defence is the hardest stat to train by far, although training defence in jail gives you a bigger boost than the other stats
Battle stats only affect how well you do in battle. Remember, for every attribute there is a counter-attribute, e.g. you may have an incredibly high amount of speed and can usually defeat/hit everyone thanks to that, but then someone might have higher dexterity, so you would be less likely to hit them. (and same with strength:defence)
Speed affects how often you hit your opponent, gives you a better chance of running away from your opponent, and lessens your chances of going to jail.
Strength affects how much damage you hit your opponent for.
Defence affects how much damage you absorb from your opponents attacks, slightly decreases your hospital times.
Dexterity affects how well you dodge your opponents attacks. It also helps your stealth, if they see you attack them, or if you see them attack you.
Raising your Battle Stats:
The main way to boost your battle stats is to train at the gym. There is currently only 2 gyms in TC:
Woody’s Work Out Club
This gym is for levels 1-9 and costs $100 for a pass. but you don’t need to buy this, because you automatically have a pass to this gym when you first start playing (you can only buy it so you can switch between the two gyms when you are level 10 or over)
This gym is for levels 10 and over, it costs $25,000 to get a pass. It is very worthwhile going to this gym. Instead of costing 5 energy to train, it will cost 10, but it costs half the amount of happy and you get more of a boost for each unit you train.
Training 1 per time and waiting for your happy to refill will result in better stat gains if you have the time to do it (see training formulas above), as opposed to using all of your energy at once.
Drugs can help raise your stats much faster.
If you are level 10 or over and still haven’t changed to Average Joe’s Gym, then do it now by going: Newspaper>Local Gyms and select “check it out”, but don’t go back to Woody’s Workout Club, it is a waste of money and time.
Another way to boost your battle stats is by using your merits. Under the non-incremental upgrades, there is an option to buy an upgrade of (10*level) of any stat you select. (so if you’re level 5 and want to buy the one that boosts your defence, it’d be 10*5, so that would be a boost of 50 defence). But this isn’t really worth it unless you are a really high level (20+ minimum).
Thanks to Sylar_  for coding the Training Calculator!