Every object has weight. But the center of its weight is not always in the middle of the object. If the top of an object is heavier than its bottom, it will fall over easily. We say that its center of gravity is high. But if the bottom is heavier, it won't fall easily. Then we say that its center of gravity is low.
    Look at the first picture. This empty box must fall over, because its center of gravity (C) is not above the line of its bottom (AB).
Now look at the second picture. There is some heavy iron in the bottom of this box. It will not fall, because its center of gravity is above its bottom.

小明所在班级有16名男生报名参加校运动会，他们的身高（单位：cm）如下：

170  165  178  166  173  163  178  172

170  174  170  170  174  178  178  178

（1）将这16名男生的身高由矮到高排列，统计每种身高的频数和频率，并填如表．

（2）身高超过170cm的同学有几名？约占总人数的百分之几？（精确到1%）