2.某小組有20名射手,其中1,2,3,4級(jí)射手分別為2,6,9,3名.又若選1,2,3,4級(jí)射手參加比賽,則在比賽中射中目標(biāo)的概率分別為0.85,0.64,0.45,0.32,今隨機(jī)選一人參加比賽,則該小組比賽中射中目標(biāo)的概率為_(kāi)_______. 【解析】設(shè)B表示“該小組比賽中射中目標(biāo)”,Ai(i=1,2,3,4)表示“選i級(jí)射手參加比賽”,則P(B)= P(Ai)P(B|Ai)= 2/20×0.85+ 6/20 ×0.64+ 9/20×0.45+ 3/20×0.32=0.527 5.答案:0.527 53.兩批相同的產(chǎn)品各有12件和10件,每批產(chǎn)品中各有1件廢品,現(xiàn)在先從第1批產(chǎn)品中任取1件放入第2批中,然后從第2批中任取1件,則取到廢品的概率為_(kāi)_______. 【解析】設(shè)A表示“取到廢品”,B表示“從第1批中取到廢品”,有P(B)= 112,P(A|B)= 2/11 ,P(A| )= 1/11所以P(A)=P(B)P(A|B)+P( )P(A| )4.有一批同一型號(hào)的產(chǎn)品,已知其中由一廠(chǎng)生產(chǎn)的占 30%, 二廠(chǎng)生產(chǎn)的占 50% , 三廠(chǎng)生產(chǎn)的占 20%, 又知這三個(gè)廠(chǎng)的產(chǎn)品次品率分別為2% , 1%, 1%,問(wèn)從這批產(chǎn)品中任取一件是次品的概率是多少?
3.某縣農(nóng)民月均收入服從N(500,202)的正態(tài)分布,則此縣農(nóng)民月均收入在500元到520元間人數(shù)的百分比約為 . 解析:因?yàn)樵率杖敕恼龖B(tài)分布N(500,202),所以μ=500,σ=20,μ-σ=480,μ+σ=520.所以月均收入在[480,520]范圍內(nèi)的概率為0.683.由圖像的對(duì)稱(chēng)性可知,此縣農(nóng)民月均收入在500到520元間人數(shù)的百分比約為34.15%.答案:34.15%4.某種零件的尺寸ξ(單位:cm)服從正態(tài)分布N(3,12),則不屬于區(qū)間[1,5]這個(gè)尺寸范圍的零件數(shù)約占總數(shù)的 . 解析:零件尺寸屬于區(qū)間[μ-2σ,μ+2σ],即零件尺寸在[1,5]內(nèi)取值的概率約為95.4%,故零件尺寸不屬于區(qū)間[1,5]內(nèi)的概率為1-95.4%=4.6%.答案:4.6%5. 設(shè)在一次數(shù)學(xué)考試中,某班學(xué)生的分?jǐn)?shù)X~N(110,202),且知試卷滿(mǎn)分150分,這個(gè)班的學(xué)生共54人,求這個(gè)班在這次數(shù)學(xué)考試中及格(即90分及90分以上)的人數(shù)和130分以上的人數(shù).解:μ=110,σ=20,P(X≥90)=P(X-110≥-20)=P(X-μ≥-σ),∵P(X-μσ)≈2P(X-μ130)=P(X-110>20)=P(X-μ>σ),∴P(X-μσ)≈0.683+2P(X-μ>σ)=1,∴P(X-μ>σ)=0.158 5,即P(X>130)=0.158 5.∴54×0.158 5≈9(人),即130分以上的人數(shù)約為9人.
解析:因?yàn)闇p法和除法運(yùn)算中交換兩個(gè)數(shù)的位置對(duì)計(jì)算結(jié)果有影響,所以屬于組合的有2個(gè).答案:B2.若A_n^2=3C_(n"-" 1)^2,則n的值為( )A.4 B.5 C.6 D.7 解析:因?yàn)锳_n^2=3C_(n"-" 1)^2,所以n(n-1)=(3"(" n"-" 1")(" n"-" 2")" )/2,解得n=6.故選C.答案:C 3.若集合A={a1,a2,a3,a4,a5},則集合A的子集中含有4個(gè)元素的子集共有 個(gè). 解析:滿(mǎn)足要求的子集中含有4個(gè)元素,由集合中元素的無(wú)序性,知其子集個(gè)數(shù)為C_5^4=5.答案:54.平面內(nèi)有12個(gè)點(diǎn),其中有4個(gè)點(diǎn)共線(xiàn),此外再無(wú)任何3點(diǎn)共線(xiàn),以這些點(diǎn)為頂點(diǎn),可得多少個(gè)不同的三角形?解:(方法一)我們把從共線(xiàn)的4個(gè)點(diǎn)中取點(diǎn)的多少作為分類(lèi)的標(biāo)準(zhǔn):第1類(lèi),共線(xiàn)的4個(gè)點(diǎn)中有2個(gè)點(diǎn)作為三角形的頂點(diǎn),共有C_4^2·C_8^1=48(個(gè))不同的三角形;第2類(lèi),共線(xiàn)的4個(gè)點(diǎn)中有1個(gè)點(diǎn)作為三角形的頂點(diǎn),共有C_4^1·C_8^2=112(個(gè))不同的三角形;第3類(lèi),共線(xiàn)的4個(gè)點(diǎn)中沒(méi)有點(diǎn)作為三角形的頂點(diǎn),共有C_8^3=56(個(gè))不同的三角形.由分類(lèi)加法計(jì)數(shù)原理,不同的三角形共有48+112+56=216(個(gè)).(方法二 間接法)C_12^3-C_4^3=220-4=216(個(gè)).
(2)方法一:第一次取到一件不合格品,還剩下99件產(chǎn)品,其中有4件不合格品,95件合格品,于是第二次又取到不合格品的概率為4/99,由于這是一個(gè)條件概率,所以P(B|A)=4/99.方法二:根據(jù)條件概率的定義,先求出事件A,B同時(shí)發(fā)生的概率P(AB)=(C_5^2)/(C_100^2 )=1/495,所以P(B|A)=(P"(" AB")" )/(P"(" A")" )=(1/495)/(5/100)=4/99.6.在某次考試中,要從20道題中隨機(jī)地抽出6道題,若考生至少答對(duì)其中的4道題即可通過(guò);若至少答對(duì)其中5道題就獲得優(yōu)秀.已知某考生能答對(duì)其中10道題,并且知道他在這次考試中已經(jīng)通過(guò),求他獲得優(yōu)秀成績(jī)的概率.解:設(shè)事件A為“該考生6道題全答對(duì)”,事件B為“該考生答對(duì)了其中5道題而另一道答錯(cuò)”,事件C為“該考生答對(duì)了其中4道題而另2道題答錯(cuò)”,事件D為“該考生在這次考試中通過(guò)”,事件E為“該考生在這次考試中獲得優(yōu)秀”,則A,B,C兩兩互斥,且D=A∪B∪C,E=A∪B,由古典概型的概率公式及加法公式可知P(D)=P(A∪B∪C)=P(A)+P(B)+P(C)=(C_10^6)/(C_20^6 )+(C_10^5 C_10^1)/(C_20^6 )+(C_10^4 C_10^2)/(C_20^6 )=(12" " 180)/(C_20^6 ),P(E|D)=P(A∪B|D)=P(A|D)+P(B|D)=(P"(" A")" )/(P"(" D")" )+(P"(" B")" )/(P"(" D")" )=(210/(C_20^6 ))/((12" " 180)/(C_20^6 ))+((2" " 520)/(C_20^6 ))/((12" " 180)/(C_20^6 ))=13/58,即所求概率為13/58.
冪函數(shù)是在繼一次函數(shù)、反比例函數(shù)、二次函數(shù)之后,又學(xué)習(xí)了單調(diào)性、最值、奇偶性的基礎(chǔ)上,借助實(shí)例,總結(jié)出冪函數(shù)的概念,再借助圖像研究?jī)绾瘮?shù)的性質(zhì).課程目標(biāo)1、理解冪函數(shù)的概念,會(huì)畫(huà)冪函數(shù)y=x,y=x2,y=x3,y=x-1,y=x 的圖象;2、結(jié)合這幾個(gè)冪函數(shù)的圖象,理解冪函數(shù)圖象的變化情況和性質(zhì);3、通過(guò)觀察、總結(jié)冪函數(shù)的性質(zhì),培養(yǎng)學(xué)生概括抽象和識(shí)圖能力.?dāng)?shù)學(xué)學(xué)科素養(yǎng)1.數(shù)學(xué)抽象:用數(shù)學(xué)語(yǔ)言表示函數(shù)冪函數(shù);2.邏輯推理:常見(jiàn)冪函數(shù)的性質(zhì);3.數(shù)學(xué)運(yùn)算:利用冪函數(shù)的概念求參數(shù);4.數(shù)據(jù)分析:比較冪函數(shù)大?。?.數(shù)學(xué)建模:在具體問(wèn)題情境中,運(yùn)用數(shù)形結(jié)合思想,利用冪函數(shù)性質(zhì)、圖像特點(diǎn)解決實(shí)際問(wèn)題。重點(diǎn):常見(jiàn)冪函數(shù)的概念、圖象和性質(zhì);難點(diǎn):冪函數(shù)的單調(diào)性及比較兩個(gè)冪值的大小.
4.寫(xiě)出下列隨機(jī)變量可能取的值,并說(shuō)明隨機(jī)變量所取的值表示的隨機(jī)試驗(yàn)的結(jié)果.(1)一個(gè)袋中裝有8個(gè)紅球,3個(gè)白球,從中任取5個(gè)球,其中所含白球的個(gè)數(shù)為X.(2)一個(gè)袋中有5個(gè)同樣大小的黑球,編號(hào)為1,2,3,4,5,從中任取3個(gè)球,取出的球的最大號(hào)碼記為X.(3). 在本例(1)條件下,規(guī)定取出一個(gè)紅球贏2元,而每取出一個(gè)白球輸1元,以ξ表示贏得的錢(qián)數(shù),結(jié)果如何?[解] (1)X可取0,1,2,3.X=0表示取5個(gè)球全是紅球;X=1表示取1個(gè)白球,4個(gè)紅球;X=2表示取2個(gè)白球,3個(gè)紅球;X=3表示取3個(gè)白球,2個(gè)紅球.(2)X可取3,4,5.X=3表示取出的球編號(hào)為1,2,3;X=4表示取出的球編號(hào)為1,2,4;1,3,4或2,3,4.X=5表示取出的球編號(hào)為1,2,5;1,3,5;1,4,5;2,3,5;2,4,5或3,4,5.(3) ξ=10表示取5個(gè)球全是紅球;ξ=7表示取1個(gè)白球,4個(gè)紅球;ξ=4表示取2個(gè)白球,3個(gè)紅球;ξ=1表示取3個(gè)白球,2個(gè)紅球.
《函數(shù)的單調(diào)性與最大(?。┲祡》系人教A版高中數(shù)學(xué)必修第一冊(cè)第三章第二節(jié)的內(nèi)容,本節(jié)包括函數(shù)的單調(diào)性的定義與判斷及其證明、函數(shù)最大(?。┲档那蠓āT诔踔袑W(xué)習(xí)函數(shù)時(shí),借助圖像的直觀性研究了一些函數(shù)的增減性,這節(jié)內(nèi)容是初中有關(guān)內(nèi)容的深化、延伸和提高函數(shù)的單調(diào)性是函數(shù)眾多性質(zhì)中的重要性質(zhì)之一,函數(shù)的單調(diào)性一節(jié)中的知識(shí)是前一節(jié)內(nèi)容函數(shù)的概念和圖像知識(shí)的延續(xù),它和后面的函數(shù)奇偶性,合稱(chēng)為函數(shù)的簡(jiǎn)單性質(zhì),是今后研究指數(shù)函數(shù)、對(duì)數(shù)函數(shù)、冪函數(shù)及其他函數(shù)單調(diào)性的理論基礎(chǔ);在解決函數(shù)值域、定義域、不等式、比較兩數(shù)大小等具體問(wèn)需用到函數(shù)的單調(diào)性;同時(shí)在這一節(jié)中利用函數(shù)圖象來(lái)研究函數(shù)性質(zhì)的救開(kāi)結(jié)合思想將貫穿于我們整個(gè)高中數(shù)學(xué)教學(xué)。
《數(shù)學(xué)1必修本(A版)》的第五章4.5.2用二分法求方程的近似解.本節(jié)課要求學(xué)生根據(jù)具體的函數(shù)圖象能夠借助計(jì)算機(jī)或信息技術(shù)工具計(jì)算器用二分法求相應(yīng)方程的近似解,了解這種方法是求方程近似解的常用方法,從中體會(huì)函數(shù)與方程之間的聯(lián)系;它既是本冊(cè)書(shū)中的重點(diǎn)內(nèi)容,又是對(duì)函數(shù)知識(shí)的拓展,既體現(xiàn)了函數(shù)在解方程中的重要應(yīng)用,同時(shí)又為高中數(shù)學(xué)中函數(shù)與方程思想、數(shù)形結(jié)合思想、二分法的算法思想打下了基礎(chǔ),因此決定了它的重要地位.發(fā)展學(xué)生數(shù)學(xué)直觀、數(shù)學(xué)抽象、邏輯推理和數(shù)學(xué)建模的核心素養(yǎng)。課程目標(biāo) 學(xué)科素養(yǎng)1.通過(guò)具體實(shí)例理解二分法的概念及其使用條件.2.了解二分法是求方程近似解的常用方法,能借助計(jì)算器用二分法求方程的近似解.3.會(huì)用二分法求一個(gè)函數(shù)在給定區(qū)間內(nèi)的零點(diǎn),從而求得方程的近似解. a.數(shù)學(xué)抽象:二分法的概念;b.邏輯推理:運(yùn)用二分法求近似解的原理;
1.確定研究對(duì)象,明確哪個(gè)是解釋變量,哪個(gè)是響應(yīng)變量;2.由經(jīng)驗(yàn)確定非線(xiàn)性經(jīng)驗(yàn)回歸方程的模型;3.通過(guò)變換,將非線(xiàn)性經(jīng)驗(yàn)回歸模型轉(zhuǎn)化為線(xiàn)性經(jīng)驗(yàn)回歸模型;4.按照公式計(jì)算經(jīng)驗(yàn)回歸方程中的參數(shù),得到經(jīng)驗(yàn)回歸方程;5.消去新元,得到非線(xiàn)性經(jīng)驗(yàn)回歸方程;6.得出結(jié)果后分析殘差圖是否有異常 .跟蹤訓(xùn)練1.一只藥用昆蟲(chóng)的產(chǎn)卵數(shù)y與一定范圍內(nèi)的溫度x有關(guān),現(xiàn)收集了6組觀測(cè)數(shù)據(jù)列于表中: 經(jīng)計(jì)算得: 線(xiàn)性回歸殘差的平方和: ∑_(i=1)^6?〖(y_i-(y_i ) ?)〗^2=236,64,e^8.0605≈3167.其中 分別為觀測(cè)數(shù)據(jù)中的溫度和產(chǎn)卵數(shù),i=1,2,3,4,5,6.(1)若用線(xiàn)性回歸模型擬合,求y關(guān)于x的回歸方程 (精確到0.1);(2)若用非線(xiàn)性回歸模型擬合,求得y關(guān)于x回歸方程為 且相關(guān)指數(shù)R2=0.9522. ①試與(1)中的線(xiàn)性回歸模型相比較,用R2說(shuō)明哪種模型的擬合效果更好 ?②用擬合效果好的模型預(yù)測(cè)溫度為35℃時(shí)該種藥用昆蟲(chóng)的產(chǎn)卵數(shù).(結(jié)果取整數(shù)).
新知講授(一)——隨機(jī)試驗(yàn) 我們把對(duì)隨機(jī)現(xiàn)象的實(shí)現(xiàn)和對(duì)它的觀察稱(chēng)為隨機(jī)試驗(yàn),簡(jiǎn)稱(chēng)試驗(yàn),常用字母E表示。我們通常研究以下特點(diǎn)的隨機(jī)試驗(yàn):(1)試驗(yàn)可以在相同條件下重復(fù)進(jìn)行;(2)試驗(yàn)的所有可能結(jié)果是明確可知的,并且不止一個(gè);(3)每次試驗(yàn)總是恰好出現(xiàn)這些可能結(jié)果中的一個(gè),但事先不確定出現(xiàn)哪個(gè)結(jié)果。新知講授(二)——樣本空間思考一:體育彩票搖獎(jiǎng)時(shí),將10個(gè)質(zhì)地和大小完全相同、分別標(biāo)號(hào)0,1,2,...,9的球放入搖獎(jiǎng)器中,經(jīng)過(guò)充分?jǐn)嚢韬髶u出一個(gè)球,觀察這個(gè)球的號(hào)碼。這個(gè)隨機(jī)試驗(yàn)共有多少個(gè)可能結(jié)果?如何表示這些結(jié)果?根據(jù)球的號(hào)碼,共有10種可能結(jié)果。如果用m表示“搖出的球的號(hào)碼為m”這一結(jié)果,那么所有可能結(jié)果可用集合表示{0,1,2,3,4,5,6,7,8,9}.我們把隨機(jī)試驗(yàn)E的每個(gè)可能的基本結(jié)果稱(chēng)為樣本點(diǎn),全體樣本點(diǎn)的集合稱(chēng)為試驗(yàn)E的樣本空間。
Teaching plan for Unit 1 book3Good morning, teachers. It’s my great pleasure to be here because I can share my lesson with you and I can learn a lot from it. I’ll begin my lesson from the following four parts, the teaching material, the teaching methods, the studying methods and the teaching procedure.Firstly, let me talk about the teaching material. The content of my lesson is the reading passage festivals and celebrations of Unit 1 Festivals around the world. This passage is about festivals and celebrations. By studying this passage, we’ll enable the students to know that festivals exit everywhere, and many of festivals in different countries celebrate similar ideas. As we all know, the reading passage is the center of each unit. If the Ss can learn it well, it will be helpful to make the Ss learn the rest of this unit.After studying the teaching material, I think the teaching aims are as the followings:1. Knowledge aims:(1) The Ss can master the usage of the important words andexpressions.(2)The Ss can use the __________________ (grammar) in the proper situation.Make students know about the festivals all over the world and the detail of the festivals, such as origin, content, and the date of the holiday festivals.2. Ability aims:(1) Students can talk about festivals and celebrations in English(2) To improve the student’s reading ability, especially their skimming and scanning ability.3. Emotion aims:Make the Ss know about the foreign festivals, and respect other countries’ custom.Next, let’s come to the important points and the difficult points.The important point is how to make the Ss understand the text better and the difficult point is how can they talk about it. secondly, Teaching Methods:1. task-based Language Teaching2. Computer assisted language teaching.3. question-and–answer methodThirdly, Studying Methods:
This teaching period mainly deals with grammar “restrictive relative clauses.” To begin with, teachers should lead students to revise what they have learned about the relative pronouns and relative adverbs. And then, teachers move on to stress more special cases concerning this grammar, such as the “preposition+ relative pronouns which and whom” and cases where we can omit the relative pronouns. This period carries considerable significance to the cultivation of students’ writing competence and lays a solid foundation for the basic appreciation of language beauty. The teacher is expected to enable students to master this period thoroughly and consolidate the knowledge by doing some exercises. 1. Guide students to review the basic usages of relative pronouns and adverbs of attributive clauses.2. Lead students to learn to use some special cases concerning restrictive relative clauses flexibly.2. Enable students to use the basic phrases structures flexibly.3. Strengthen students’ great interest in grammar learning.1. Help students to appreciate the function of relative pronouns and adverbs of attributive clauses in a sentence2. Instruct students to write essays using the proper relative pronouns and adverbs of attributive clauses.本節(jié)語(yǔ)法思考:定語(yǔ)從句在復(fù)合句中的作用是什么? 關(guān)系詞有哪些?定語(yǔ)從句在復(fù)合句中的作用相當(dāng)于形容詞,它在句中作定語(yǔ)修飾名詞或代詞。他們?cè)谙刃性~和定語(yǔ)從句之間起到聯(lián)系作用,同時(shí)在意義上代表先行詞并在定語(yǔ)從句中擔(dān)任一個(gè)成分。被定語(yǔ)從句所修飾的詞稱(chēng)先行詞,定語(yǔ)從句一般放在先行詞的后面。
The theme of the reading and thinking is about “Understanding how a problem was solved”.The Listening & Speaking & Talking is about international co-work to protect the Mount Tai, in which the students from seven countries came up with many solutions even create the Mount Tai App. This section aims at showing how to solve a difficult and even tough problem about protecting the cultural heritage by the international co-work. So in this section, cultivating students’ international awareness is very clear and important. Concretely, with the economic development, how to balance the protection of cultural relics and social development is a big challenge for human. In the 1950s, the Egyptian government wanted to build the Aswan Dam across the Nile to control floods, produce electricity and water farms. But the proposal led to protests because it would destroy a lot of cultural relics. The Egyptian had no choice but ask the UN for help. Therefore, a international cooperation about how to protect the cultural relics began, which involved the time length about 20 years and a large amount of fund. Then, the problems was solved. 1. Read quickly to get the main idea and the structure of the article; read careful to get detailed information.2. Learn to use the reading strategy---making a timeline3. Learn how to solve a tough problem by asking for help and cooperation4. Have the international awareness and understand the great strength of international cooperation.1. Read quickly to get the main idea and the structure of the article; read careful to get detailed information.2. Learn to use the reading strategy---making a timeline.3. Learn how to solve a tough problem by asking for help and cooperation.
二、說(shuō)學(xué)情本課的教學(xué)對(duì)象為高二學(xué)生,他們思維活躍已具備一定歸納能力和分析、綜合能力,能夠自主地分析現(xiàn)實(shí)生活中的一些文化行為,但看問(wèn)題往往比較偏激、片面,缺乏良好的邏輯思維能力。所以,在文化創(chuàng)新的途徑上要對(duì)他們進(jìn)行指導(dǎo),以免走入誤區(qū)。三、教學(xué)目標(biāo)根據(jù)新課程標(biāo)準(zhǔn)、教材特點(diǎn)、學(xué)生的實(shí)際,我確定了如下教學(xué)目標(biāo):【知識(shí)與能力目標(biāo)】1.理解文化創(chuàng)新的根本途徑和兩個(gè)基本途徑;2.了解文化創(chuàng)新過(guò)程中需要堅(jiān)持正確方向,克服錯(cuò)誤傾向。
This unit is about the Internet, which has a great influence to our humans and our lives. During the Listening & Speaking & Talking and Reading and Thinking section, the influence in examples has been shown. Thus, use the Present Perfect Tense is appropriate. However, in order to show the justice or weaken the doer of the behavior/action, it’s better to use the Present Perfect Passive Voice than the Present Perfect Tense. Besides, having learned to use the Present Perfect Passive Voice, students can beautify their language in their writing. 1. Learn the structure of the Present Perfect Passive Voice and its functions. 2. Learn to change the sentences with the Present Perfect Passive Voice into the sentences with the Present Perfect Passive Voice. 3. Learn to write sentences with the Present Perfect Passive Voice flexibly according to the context. 1. Learn the structure of the Present Perfect Passive Voice and its functions. 2. Learn to change the sentences with the Present Perfect Passive Voice into the sentences with the Present Perfect Passive Voice. 3. Learn to write sentences with the Present Perfect Passive Voice flexibly according to the context. Step 1 Observe the following sentences, then change the sentences into passive voice.He has been selected to take part in the sports meeting.(肯定句)他已被挑選出來(lái)參加運(yùn)動(dòng)會(huì)。The ink has not been removed from his overcoat.(否定句)墨跡還沒(méi)有從他外套上去掉。
Listening and Speaking introduces the topic of “ask about online habits”. Many middle school students have been surfing the Internet for many years, but what they do with the Internet and how much time they spend every day may not be very clear to themselves, nor to other students. This section allows students to investigate their peers' Internet use, which is conducive to their mutual understanding and understanding of the Internet. It can also help them reflect on their own online behavior, learn from other people's good online habits, and get rid of their bad online behavior.The listening text of this section is an investigation interview. The investigators interview specific groups with the same questions to obtain information, so as to understand their views, practices or attitudes on this issue. There are two specific questions: “how much time do you spend online every day? What do you usually do online?”. The answers of the three respondents provide rich and different information, and achieve the purpose of the investigators. The oral discourse structure of survey interviews generally includes greeting and explaining the purpose of the interview, presenting the interview questions and the respondents' answers. Listening and Talking introduces the theme of “choosing the right application ". Listening text is a conversation between Laura and Xiao Bo. In this part of listening, “oink”; “piggy bank” may cause the students' hearing comprehension limitation. Oink refers to sound word and pig's sound. So, add some oink to my piggy bank is often used to describe "making a little money".1. Guide students to understand the content of listening texts in terms of listening for definitions.2. Cultivate students' ability to define words and understand an investigation interview.
Paragraph 3. Jan decided to start an IT club to teach old people how to use computers and the Internet. Paragraph 4. Jan has started taking online classes to learn more about how to use the Internet to make society better. Paragraph 5. Jan’s life has been greatly improved by the Internet. Step 5: Critical thinking:(1)How do you arrange your time spent on study and the Internet? Is it reasonable? I usually surf the Internet using my mobile phone for only an hour after class, and it is reasonable for me.(2)What are your online activities? Are they safe? I chat with my friends, read news and play games. I never give away my private information so I think they are safe.Step 4: summary Much has been written about the wonders of the World Wide Web. There are countless articles (1)______(tell) us how the Internet has made our lives more convenient. But the Internet has done a lot (2)_____(much) for people than simply make life more convenient. People’s lives (3) _________________(change) by online communities and social networks so far. Take Jan for example, who developed a serious illness that made her (4)_____(stick) at home with only her computer to keep (5)___(she) company. She joined an online group (6)______ she could share problems, support and advice with others. She considered the ability to remove the distance between people as one of the greatest (7)_______(benefit). She was so inspired (8)____ she started an IT club in which many people have been helped. She has started to learn more about how to use the Internet to make society better. Her next goal is to start a charity website to raise money (9)___ children in poor countries. Jan’s life has been (10)______(great) improved by the Internet. Step 5 Homework:Review what we have learned and find out the key language points in the text.
⑦identity theft 身份盜竊⑧chat room 聊天室⑨draft your blog post 起草博客帖子⑩post embarrassing photos 張貼尷尬照片 【話(huà)題句式】 1. How do you stay safe online and avoid bad experiences on the Internet? 你如何在網(wǎng)上保持安全, 避免在網(wǎng)上的不良經(jīng)歷? 2. I’m not an expert, but many years as a blogger have taught me a thing or two. 我不是專(zhuān)家, 但作為一個(gè)博主, 我已經(jīng)學(xué)了好幾年了。 3. If you see or read something that makes you feel uncomfortable, leave the site immediately. 如果你看到或讀到一些讓你覺(jué)得不舒服的東西, 立即離開(kāi)這個(gè)網(wǎng)站。4. Don’t give out your address or phone number. 別告訴別人你的地址或電話(huà)號(hào)碼。 5. Identity theft is a common and serious problem. 身份盜竊是一個(gè)常見(jiàn)而嚴(yán)重的問(wèn)題。6. Being online is no excuse for being rude, and you don’t want to become a target for a troll or cyberbully. 上網(wǎng)并不是無(wú)禮的借口, 你也不想成為發(fā)挑釁帖子的人或網(wǎng)絡(luò)惡霸的目標(biāo)。 7. Trolls often use several false names so that they can stay on a site. 發(fā)挑釁帖子的人經(jīng)常使用幾個(gè)假名, 這樣他們就可以留在一個(gè)網(wǎng)站上。8. However, the more polite you are, the less likely it is you will be attacked. 然而, 你越有禮貌, 你被攻擊的可能性就越小。
由樣本相關(guān)系數(shù)??≈0.97,可以推斷脂肪含量和年齡這兩個(gè)變量正線(xiàn)性相關(guān),且相關(guān)程度很強(qiáng)。脂肪含量與年齡變化趨勢(shì)相同.歸納總結(jié)1.線(xiàn)性相關(guān)系數(shù)是從數(shù)值上來(lái)判斷變量間的線(xiàn)性相關(guān)程度,是定量的方法.與散點(diǎn)圖相比較,線(xiàn)性相關(guān)系數(shù)要精細(xì)得多,需要注意的是線(xiàn)性相關(guān)系數(shù)r的絕對(duì)值小,只是說(shuō)明線(xiàn)性相關(guān)程度低,但不一定不相關(guān),可能是非線(xiàn)性相關(guān).2.利用相關(guān)系數(shù)r來(lái)檢驗(yàn)線(xiàn)性相關(guān)顯著性水平時(shí),通常與0.75作比較,若|r|>0.75,則線(xiàn)性相關(guān)較為顯著,否則不顯著.例2. 有人收集了某城市居民年收入(所有居民在一年內(nèi)收入的總和)與A商品銷(xiāo)售額的10年數(shù)據(jù),如表所示.畫(huà)出散點(diǎn)圖,判斷成對(duì)樣本數(shù)據(jù)是否線(xiàn)性相關(guān),并通過(guò)樣本相關(guān)系數(shù)推斷居民年收入與A商品銷(xiāo)售額的相關(guān)程度和變化趨勢(shì)的異同.
對(duì)于離散型隨機(jī)變量,可以由它的概率分布列確定與該隨機(jī)變量相關(guān)事件的概率。但在實(shí)際問(wèn)題中,有時(shí)我們更感興趣的是隨機(jī)變量的某些數(shù)字特征。例如,要了解某班同學(xué)在一次數(shù)學(xué)測(cè)驗(yàn)中的總體水平,很重要的是看平均分;要了解某班同學(xué)數(shù)學(xué)成績(jī)是否“兩極分化”則需要考察這個(gè)班數(shù)學(xué)成績(jī)的方差。我們還常常希望直接通過(guò)數(shù)字來(lái)反映隨機(jī)變量的某個(gè)方面的特征,最常用的有期望與方差.二、 探究新知探究1.甲乙兩名射箭運(yùn)動(dòng)員射中目標(biāo)靶的環(huán)數(shù)的分布列如下表所示:如何比較他們射箭水平的高低呢?環(huán)數(shù)X 7 8 9 10甲射中的概率 0.1 0.2 0.3 0.4乙射中的概率 0.15 0.25 0.4 0.2類(lèi)似兩組數(shù)據(jù)的比較,首先比較擊中的平均環(huán)數(shù),如果平均環(huán)數(shù)相等,再看穩(wěn)定性.假設(shè)甲射箭n次,射中7環(huán)、8環(huán)、9環(huán)和10環(huán)的頻率分別為:甲n次射箭射中的平均環(huán)數(shù)當(dāng)n足夠大時(shí),頻率穩(wěn)定于概率,所以x穩(wěn)定于7×0.1+8×0.2+9×0.3+10×0.4=9.即甲射中平均環(huán)數(shù)的穩(wěn)定值(理論平均值)為9,這個(gè)平均值的大小可以反映甲運(yùn)動(dòng)員的射箭水平.同理,乙射中環(huán)數(shù)的平均值為7×0.15+8×0.25+9×0.4+10×0.2=8.65.