Sorry but you need to read up on your statistics. There is a very high paying field of mathematics to deal with exactly this kind of stuff.Zer_ said:That depends, I mean sure the more subjects you have the higher the chances that the average will be closer to the mean heart rate for homo sapiens, but it still has a chance to skew results, especially considering that some people have some rather quick heart rates.
That's not taking into consideration the different psychological reactions that people get from games (I'm not saying people who play games are psycho, but everyone has a slightly different reaction to games).
Basically, it doesn't matter if some people are higher or lower, because if you have randomly sampled enough people and put them into two groups, they will have very close to the same average. The more people you get, the closer the two groups will be to each other. Now, if you perform some kind of manipulation on one group but not the other (such as having one group play videogames and the other not) any deviation in the averages must be, in some way, caused by the manipulation you performed.
As for whether the heart rate goes up or down, it's pretty well known that for a vast majority of people, showing them gory images will cause them to release adrenaline. It's part of everyone's "fight or flight" response to potential danger. Some rare people are perhaps going to be neutrally or even negatively affected, but on average people will go up. So once again, on average the change should have been the same from one group to the other. Since the difference in change was non-zero, it must have been related to the manipulation in some way.