一组数据 41 61 61 62 62 63 64 64 65 65 66 66 67 68 71 71 71 73 74 75 77 79 81 81 一共24个 问:a)Z-score of 75b) In what percentile is the value 71c) what is the value of the 25th percentile?怎么求呢 求出来代表什么呢?谢谢~