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已知样本数据：98，99，100，101，102．则它们的标准差是 ．
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某工厂对一批产品进行了抽样检测.如图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品
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下列数据是从一个总体中抽取的一个样本1011021039998100求得样本方差为
数据9899100101102的方差是．
为了考察某校各班参加课外书法小组的人数从全校随机抽取5个班级把每个班级参加该小组的人数作为样本数据已
某工厂对一批产品进行了抽样检测右图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品净
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某工厂对一批产品进行了抽样检测下图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品净
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为了考察某校各班参加课外书法小组的人数在全校随机抽取5个班级把每个班级参加该小组的认为作为样本数据.
样本频数分布反映了
样本数据的多少
样本数据的平均水平
样本数据的离散程度
样本数据在各个小范围内数量的多少
观察下列各式计算3×1×2+2×3+3×4++99×100=
97×98×99
98×99×100
99×100×101
100×101×102
已知一组同学练习射击击中靶子的环数分别为10398991011009897104计算它们的方差
已知样本x99100101y的平均数为100方差是2则x=y=.
为了考察某校各班参加课外书法小组的人数在全校随机抽取5个班级把每个班级参加该小组的人数作为样本数据.
.某工厂对一批产品进行了抽样检测.下图是根据抽样检测后的产品净重单位:克数据绘制的频率分布直方图其中
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某工厂对一批产品进行了抽样检测右图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品净
某工厂对一批产品进行了抽样检测.右图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品
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已知样本为1019810210099则样本方差为
2
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样本数据1816151620的方差＝______.
某工厂对一批产品进行了抽样检测.右图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品
某工厂对一批产品进行了抽样检测如图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品
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某工厂对一批产品进行了抽样检测.右图是根据抽样检测后的产品净重单位克数据绘制的频率分布直方图其中产品
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某兴趣小组利用如图1所示的装置来“探究合外力的功与物体动能变化的关系”．他们通过改变光电门的位置和悬挂物的质量进行多次实验采集多组数据．已知将此装置平衡摩擦后小车总是由同一位置自由释放小车上方固定一宽度为d的挡光板． 1下列关于操作中的说法正确的是．多选 A．调整轨道的倾角至合适位置的标志是悬挂物连带小车在轨道上匀速运动 B．实验时使悬挂物的质量远小于小车的质量就可以近似认为悬挂物的重力等于小车所受拉力 C．实验时务必先接通光电门待其正常工作后再释放小车 D．多次实验时一定要让小车由静止释放 2本小组同学在实验中有不同操作和数据处理方式你认为合理的说法是．多选 A．甲同学把小车的末速度v作为横坐标拉力对小车做的功W作为纵坐标作出图线后再分析得出结论 B．乙同学保持悬挂物的质量不变以小车的位移x作为纵坐标以小车的末速度的平方v2作为横坐标作出图线后能得出结论 C．丙同学保持小车的位移不变以悬挂物的质量m'为纵坐标以小车的末速度的倒数作为横坐标作出图线后能得出结论 D．丁同学保持小车的位移不变以悬挂物的质量m'为纵坐标以小车和悬挂物的获得的总动能作为横坐标作出图线后能得出结论 3测量挡光板的宽度时游标卡尺的示数如图2所示则其宽度为． 4戊同学对实验数据进行分析．他把小车和悬挂物作为研究对象悬挂物的重力作为合力计算出的结果始终是悬挂物重力做的功小于小车和悬挂物整体动能的增量即没能得到“合力对物体做的功等于物体动能的增量”你认为导致此结果的主要原因是．
设函数fx=． 1求f-1f0f2的值 2求不等式fx≤2的解集．
已知函数y=x-|lnx|的两个零点为x1x2且x1＞x2则
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在平面直角坐标系中直线l的参数方程为其中t为参数．现以坐标原点为极点x轴的非负半轴为极轴建立极坐标系曲线C的极坐标方程为ρ=6cosθ． 1写出直线l的普通方程和曲线C的直角坐标方程 2若点P坐标为-10直线l交曲线C于AB两点求|PA|+|PB|的值．
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计算log43+1og83log32+log92=
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定义一种集合运算A⊗B={x|x∈A∪B且x∉A∩B}设M={x||x|＜2}N={x|x2-4x+3＜0}则M⊗N=
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Haveyoueverheardthestoryofthefour﹣minutemile?ForyearspeoplebelievedthatitisimpossibleforahumanbeingtorunamileinlessthanfourminutesuntilRogerBanisterproveditwrongin1954.Withinoneyear37runnersbrokethebeliefbarrier.Andtheyearafterthat300otherrunnersdidthesamething. Whathappensifyouputananimalinapond?Anyanimalbigorsmallwillswimitswaythrough.Whathappens1someonewhodoesnotknowhowtoswimfallsindeepwaters?Youdrown.Ifananimalwhohasnotlearnedswimmingcouldescapebyswimmingwhynotyou?Becauseyoubelieveyouwilldrown2theanimaldoesnot. Thesecasesshowthepowerofbeliefs.Thereisnoother3powerfulforceindirectinghumanbehaviorthanbelief.Ourbeliefshavethepowertocreateandtodestroy. Inawayitisourbeliefs4determinehowmuchwe'llbeabletorealizeourpotential.Sopayattentiontosomeofyourbeliefs.Doyoubelieveyouareweakinmathematics?Doyoubelievethatotherpeopledislikeyou?Doyoubelievelifeisfullofproblems? Beliefisnotmysterioushoweverit'snothingbutthegeneralizationofapastincident.Asakidifadogbityouyoubelievedalldogstobedangerous.5changecertainbehavioridentifythebeliefs6associatewithit.Changethosebeliefsandanewpattern7create.
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A.womanheldherphonetightlytoherheartthewayachurch﹣goermightholdaBible.Shewasanxioustotakeapictureofanimpressivebunchofflowersthatsatnotsofarawaybutfirstshehadtogetthroughacrowdofotherspushingtheirwaytodothesame.ThecauseofthiswasBouquetstoArtoneofthemostpopulareventsatthedeYoungMuseuminSanFrancisco. Flowersellerswereaskedtocreateflowerarrangementsthatrespondtopiecesofartondisplayfromancientcarvingstocontemporarysculptures.It'sextremelyattractiveandalsomemorabletothepointthatithasbecomeaproblem. InrecentyearsthedeYoungreceivedmorethanathousandcomplaintsfrompeoplewhofeltthatcellphoneshadspoiledtheirexperienceoftheexhibit.institutionsoffineartaroundtheworldfacesimilarproblemsasthedesiretotakephotographsbecomesahugeattractionformuseumsaswellassomethingthatupsetssomeoftheirpatrons资助人.SothedeYoungrespondedwithakindofcompromisecarvingoutphotofreehoursduringtheexhibition'ssix﹣dayrun. Onecommoncomplaintabouttheeffectofsocialmediaonmuseumcultureisthatpeopleseemtobemissingoutonexperiencesbecausetheyaresobusycollectingevidenceofthem.AstudyrecentlypublishedinthejournalPsychologicalSciencesuggeststhereissometruthtothis.Itfindsthatpeoplewhokeeptakingphotosofanexhibitandpostingthemonsocialmediaratherthansimplyobservingithaveahardtimerememberingwhattheysee.Buttheissueiscomplexfortheprofessionalsrunningmuseums.LindaButlerthedeYoung'sheadofmarketingandvisitorexperienceacknowledgesthatnoteveryonewantsamuseumtobeaphoto﹣takingplayland.Yetalotofpeopledo‑andshebelievesthatthedeYoungisinnopositiontojudgeonereasonforbuyinga＄28tickettobemorevalidthananother.Ifweremovedsocialmediaandphotographyshesayswewouldriskbecomingirrelevant. 1WhatwasthewomaneagertodoaccordingtoParagraph1? A.Togetherphone. B.Totakeaphoto. C.Toescapethecrowd. D.Topushahead. 2HowdidthedeYoungrespondtothedilemma? A.Bysettingperiodswithoutphoto﹣taking. B.Bymakingtheexhibitionfreeofcharge. C.Bycompromisingwiththegovernment. D.Byextendingthefreeexhibitionhours. 3Therecentstudyfindsthattheuseofsocialmediainmuseumsmay. A.uncoverthetruth B.playanegativerole C.accumulateevidence D.causemanycomplaints 4WhichofthefollowingmayLindaButlersupport? A.Cateringtovisitors. B.Reducingadmissionprices. C.Reservingjudgementinpublic. D.Banningsocialmediaandphotography.
一位母亲根据儿子3～9岁身高的数据建立了身高ycm与年龄x岁的回归模型为=7.19x+73.93用这个模型预测这个孩子10岁时的身高则正确的叙述是
Prettyinpinkadultwomendonotrememberbeingsoobsessedwiththecolouryetitiswidespreadinouryounggirls'lives.Itisnotthatpinkinherently内在地badbutitissuchatinysliceoftherainbowandthoughitmaycelebrategirlhoodinonewayitalsorepeatedlyandfirmlyblendsgirls'identitytoappearance.Thenitpresentsthatconnectionevenamongtwo﹣year﹣oldsbetweengirlsasnotonlyinnocentbutasevidenceofinnocence.LookingaroundIdespairedattheextremelackofimaginationaboutgirls'livesandinterests. Girls'attractiontopinkmayseemunavoidablesomehowencodedintheirDNAbutaccordingtoJoPaolettianassociateprofessorofAmericanStudiesit'snot.Childrenwerenotcolour﹣codedatalluntiltheearly20thcenturyintheerabeforedomesticwashingmachinesallbabiesworewhiteasapracticalmattersincetheonlywayofgettingclothescleanwastoboilthem.What'smorebothboysandgirlsworewhatwerethoughtofasgender﹣neutraldresses.Whennurserycolourswereintroducedpinkwasactuallyconsideredthemoremasculinecolouradelicateversionofredwhichwasassociatedwithstrength.Bluewithitsintimations暗示oftheVirginMary圣母玛利亚constancyandfaithfulnesssymbolisedfemininity女性化.Itwasnotuntilthemid﹣1980swhenenlargedageandsexdifferencesbecameadominantchildren'smarketingstrategythatpinkfullycameintoitsownwhenitbegantoseeminherentlyattractivetogirlspartofwhatdefinedthemasfemaleatleastforthefirstfewcriticalyears. Ihadnotrealisedhowprofoundlymarketingtrendsinfluencedourperceptionofwhatisnaturaltorelativesincludingourcorebeliefsabouttheirpsychologicaldevelopment.TakingthetoddlerasanexampleIassumedthatphasewassomethingexpertsdevelopedafteryearsofresearchintochildren'sbehaviourwrong.ItturnsoutaccordingtoDanielCookahistorianofchildhoodconsumerismitwaspopularizedasamarketinggimmickbyclothingmanufacturersinthe1930s. Tradepublicationscounseled劝告departmentstoresthatinordertoincreasesalestheyshouldcreateathirdsteppingstonebetweeninfantwearandolderkids'clothes.Itwasonlyaftertoddler学步的小孩becamecommonshoppers'termthatitevolvedintoabroadlyaccepteddevelopmentalstage.Splittingkidsoradultsintoever﹣tiniercategorieshasprovedasafewaytoboostprofits.Andoneoftheeasiestwaystocutupamarketistomagnifygenderdifferences﹣orinventthemwheretheydidnotpreviouslyexist. 1Bysayingitis…therainbowline3Para1theauthormeanspink. A.shouldnotbethesolerepresentationofgirlhood B.shouldnotbeassociatedwithgirls'innocence C.cannotexplaingirls'lackofimagination D.cannotinfluencegirls'livesandinterests 2WhatdoesthewordencodeinPara.2referto? A.discovered B.programmed C.marked D.sealed 3Theauthorsuggeststhatourperceptionofchildren'spsychologicaldevelopmentwasmuchinfluencedby. A.themarketingofproductsforchildren B.theobservationofchildren'snature C.researchesintochildren'sbehavior D.studiesofchildhoodconsumption 4WemaylearnfromParagraph4thatdepartmentstoreswereadvisedto. A.focusoninfantwearandolderkids'clothes B.attachequalimportancetodifferentgenders C.classifyconsumersintosmallergroups D.createsomecommonshoppers'terms 5Itcanbeconcludedthatgirls'attractiontopinkseemstobe. A.clearlyexplainedbytheirinborntendency B.fullyunderstoodbyclothingmanufacturers C.mainlyimposedbyprofit﹣drivenbusinessmen D.wellinterpretedbypsychologicalexperts
函数fx=的定义域为
DidTheEarthMoveForYou? Eleven﹣year﹣oldAngelasufferedfromadiseaseinvolvinghernervoussystem.Shewasunableto1andhermovementwasrestrictedinotherwaysaswell.Thedoctorsdidnotholdoutmuch2ofhereverrecoveringfromthisillness.They3she'dspendtherestofherlifeinawheelchair.Theysaidthat4ifanywereabletocomebacktonormalaftercatchingthisdisease.Butthelittlegirlwasbraveandconfident.Therelyinginherhospitalbedshewould5toanyonewho‟dlistenthatshewasdefinitelygoingtobewalkingagainsomeday. ShewasthensenttoaspecializedrehabilitationhospitalintheSanFranciscoBayarea. Whatevertherapies治疗方法couldbe6tohercasewereused.Thingsdidn'tworkasthetherapistsexpected.Stilltheywerecharmedbyher7spirit.Theytaughtherabout 8﹣aboutseeingherselfwalking.Ifitwoulddonothingelseitwould9giveherhopeandsomething10todointhelongwakinghoursinherbed. Angelawouldworkashardaspossibleinphysicaltherapyinwhirlpoolsandinexercisesessions.Andsheworkedjustashardlyingthere11doingherimagingvisualizingherselfmovingmovingmoving! Onedayasshewastwistingwithallher12toimagineherlegsmovingagainitseemedasthougha13thinghappenedThebedmoved!Itbegantomovearoundtheroom!She14outLookwhatI'mdoing!Look!Look!I15it!Imoved! Ofcourseatthisverymomenteveryoneelseinthehospitalwasscreamingtooandrunningfor16.Peoplewerescreamingequipmentwas17andglasswasbreaking.YouseeitwastherecentSanFranciscoearthquake.Butdon‟ttellthattoAngela. She's18thatshedidit.Andnowonlyafewyearslatershe'sbackinschool. 19herowntwolegs.Nocrutches拐杖nowheelchair.YouseeanyonewhocanshaketheearthbetweenSanFranciscoandOaklandcanconqueralittledisease.Youneverknowwhat‟saroundthecorneruntilyoutakea20step. 1A.hear B.speak C.walk D.see 2A.pride B.hope C.regret D.pity 3A.predicted B.forgot C.denied D.promised 4A.some B.few C.many D.all 5A.apologize B.appeal C.refer D.swear 6A.applied B.appointed C.compared D.explained 7A.competitive B.independent C.sensitive D.undefeatable 8A.concentrating B.summarizing C.picturing D.sorting 9A.inadvance B.forsomereason C.onthecontrary D.atleast 10A.positive B.attractive C.familiar D.boring 11A.gratefully B.faithfully C.hopelessly D.royally 12A.might B.interest C.fame D.need 13A.normal B.magical C.funny D.simple 14A.found B.screamed C.turned D.counted 15A.understood B.refused C.made D.decided 16A.cover B.comfort C.freedom D.office 17A.exploding B.working C.self﹣repairing D.falling 18A.persuaded B.ashamed C.convinced D.worried 19A.By B.With C.On D.For 20A.cautious B.reasonable C.final D.further
欧拉公式eix=cosx+isinxi为虚数单位是由瑞士著名数学家欧拉发明的它将指数函数的定义域扩大到复数建立了三角函数和指数函数的关系它在复变函数论里占有非常重要的地位被誉为“数学中的天桥”根据欧拉公式可知e2i表示的复数在复平面中位于
如图所示宽L＝2m足够长的金属导轨MN和M′N′放在倾角为θ＝30°的斜面上在N和N′之间连接一个R＝2.0Ω的定值电阻在AA′处放置一根与导轨垂直质量m＝0.8kg电阻r＝2.0Ω的金属杆杆和导轨间的动摩擦因数μ＝导轨电阻不计导轨处于磁感应强度B＝1.0T方向垂直于导轨平面的匀强磁场中．用轻绳通过定滑轮将电动小车与杆的中点相连滑轮与杆之间的连线平行于斜面开始时小车位于滑轮正下方水平面上的P处小车可视为质点滑轮离小车的高度H＝4.0m．启动电动小车使之沿PS方向以v＝5.0m/s的速度匀速前进当杆滑到OO′位置时的加速度a＝3.2m/s2AA′与OO′之间的距离d＝1m求 1该过程中通过电阻R的电量q 2杆通过OO′时的速度大小 3杆在OO′时轻绳的拉力大小 4上述过程中若拉力对杆所做的功为13J求电阻R上的平均电功率．
绝热气缸倒扣在水平地面上缸内装有一电热丝缸内有一光滑的绝热活塞封闭一定质量的理想气体活塞下吊着一重为G的重物活塞重为G0活塞的截面积为S开始时封闭气柱的高为h气体的温度为T1大气压强为p0．现给电热丝缓慢加热若气体吸收热量Q时活塞下降了h求 ①气体的温度升高多少 ②气体的内能增加多少
如图所示顶端装有定滑轮的斜面体放在粗糙水平地面上AB两物体通过细绳连接并处于静止状态不计绳的质量和滑轮轴的摩擦．现用水平向右的力F作用于物体B上将物体B缓慢拉高一定的距离此过程中斜面体与物体A仍然保持静止．在此过程中
执行如图程序框图若输入的x的值为1则输出的n的值为．
在同一匀强磁场中α粒子He和质子H做匀速圆周运动若它们的动量大小相等则α粒子和质子
在各项均为正数的数列{an}中a1=a且an+1=． 1当a3=2时求a的值 2求证当n≥2时an+1≤an
下列函数是奇函数的是
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