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1、25.4 课题学习 键盘上字母的排列规律,人教版初中数学九年级上册 第二十五章概率初步,学习目标,1. 熟练用统计频率来计算概率； 2.学习利用概率解决实际生活问题； 3.领会和理解用实验检验猜想的方法； 4.培养学习兴趣。,实物导入,电脑键盘,上节回顾,前几节课我们学习了 1.事件的分类？和随机事件的概率？ 2.概率的计算方法？ 利用列表法计算概率？ 利用频率来计算概率？,置疑,电脑键盘为什么不按照字母顺序来排列呢？打乱以后不仅记起来麻烦，用起来也不方面，很多同学打字时找不着相应的字母？这里有什么原因呢？,探究活动一,为回答上面的问题，我们会想到字母的主要作用是用于书面表达英文有26个字母，
2、在通常的书面表达中，这些字母一样重要吗？在通常的英文书面表达中，各个字母出现概率各是多少？哪些字母出现的概率较大？,探究活动一,Let us take the stuff home, the boy said. So I can get the cast net and go after the sardines.They picked up the gear from the boat. The old man carried the mast on his shoulder and the boy carried the wooden bo,4 with the coiled, hard-
3、braided brown lines, the gaff and the harpoon with its shaft. The box with the baits was under the stern of the skiff along with the club that was used to subdue the big fishwhen they were brought alongside. No one would steal from the old man but it was better to take the sail and the heavy lines h
4、ome as the dew was bad for them and, though he was quite sure no local people would steal from him, the old man thought that a gaff and a harpoon were needless temptations to leave in a boat. They walked up the road together to the old mans shack and went in through its open door. The old man leaned
5、 the mast with its wrapped sail against the wall and the boy put the box and the other gear beside it. The mast was nearly as long as the one room of the shack. The shack was made of the tough budshields of the royal palm which are called guano and in it there was a bed, a table, one chair, and a pl
6、ace on the dirt floor to cook with charcoal. On the brown walls of the flattened, overlapping leaves of the sturdy fibered guano there was a picture in color of the Sacred Heart of Jesus and another of the Virgin of Cobre. These were relics of his wife. Once there had been a tinted photograph of his
7、 wife on the wall but he had taken it down because it made him toolonely to see it and it was on the shelf in the corner under his clean shirt. 摘自老人与海作者海明威,利用电脑统计,总字符：1595 总字数：1278 空格数：1595-1278 =317,字母a（包括大写）共有114个,其他字母,这里由于时间关系，我们简单举例,根据上表把这些字母和空格键按出现频率由大到小列出,现实中，有人作过大量统计并制出了下面一份频率统计表,空格 E T O A N
8、 I R S H D L C F U M P W Y G B V K X J Q Z,结论,请你根据以上统计说明“空格”键为什么设计在键盘的下方中央的位置？ 因为使用频率最高，不但放在最中央，而且是键盘中最长的键。 相反，字母“Z”最不常用，同学们还可以用英语词典查一查字母Z开头的单词数量，来加以验证。,探究活动二,请同学们采用合作学习的形式，适当分工，对英语教科书进行统计，计算各字母在书中出现的频率，并由频率估计这些字母出现的概率各是多少你们发现哪个字母的出现概率最大？,提示：选取一部分样本来统计,不仅英文，汉字也是这样，不同汉字的使用频率也不相同，在计算机上使用汉语拼音输入法时，输入同样的拼音，会显示一系列同音的汉字例如输入dian，会显示“1：点 2：店 3：电 4：垫5： ”这些同音字的排列顺序是根据什么道理呢？这与汉字的使用概率有关吗？,请对上面的问题进行分析，并通过统计方法加以检验。,巩固练习,小结,本节课我们学习了 1.通过探索键盘的规律，发现概率在生活中应用广泛； 2.在大量的偶然之中存在着必然的规律； 3.对生活中的一些不确定情况作出自己的决策； 4.用样本估计总体的统计思想及概率思想。,作业：见课后练习题,拓展：课后链接,再见！,这节课就到这里,
