Question

【题目】电脑键盘上的字母为何不按顺序排列？请你来做一项统计，下面是一篇小短文，根据短文中字母a，b出现的机会完成后面提出的问题：
Two Trips
Jack brought a small plane and began to fly it． He soon became excited and made his plane all kinds of tricks．
Jack had a friend，named Tom． One day Jack said to him，“I will pick you up in my plane．““I will be glad to．'answered Tom． They went up，and Jack flew around for half an hour and did all kinds of tricks in the air． Then they came down． Tom was to be back safely，and said to Jack，“Well，Jack，thank you very much for those two trips in your plane．“Jack was very surprised and asked，“Two trips？““Yes，my first and my last．'an﹣swered Tom．
根据上文填表

出现字母的个数	100	150	200	250	300	350	400
出现字母a的频数
出现字母a的频率
出现字母b的频数
出现字母b的频率

Answer 1

【答案】解：如图所示：

出现字母的个数	100	150	200	250	300	350	400
出现字母a的频数	12	18	23	28	36	38	45
出现字母a的频率	0.12	0.12	0.115	0.112	0.12	0.109	0.113
出现字母b的频数	3	3	4	4	6	6	6
出现字母b的频率	0.03	0.02	0.02	0.018	0.02	0.017	0.015

【解析】根据频数的概念及频率的计算方法：频率=求解．
【考点精析】掌握频数与频率是解答本题的根本，需要知道落在各个小组内的数据的个数为频数；每一小组的频数与数据总数（样本容量n）的比值叫做这一小组的频率．