During the summer holiday, my grandparents went to China. First they flew to Beijing from London. Then they went to Guangzhou by train.

    When they wentto my home, I wanted to help my grandpa carry his heavy bag, but he did himself.  They bought many presents for us.  I got a dress.  My brother got a toy plane. They brought many dried fruits for us, which they grew by themselves. My grandparents are farmers. They are hard-working people.

两名同学进行了10次三级蛙跳测试，经计算，他们的平均成绩相同，若要比较这两名同学的成绩哪一位更稳定，通常还需要比较他们成绩的（　　）