stata考試復(fù)習(xí)題庫stata考試復(fù)習(xí)題庫stata考試復(fù)習(xí)題庫xxx公司stata考試復(fù)習(xí)題庫文件編號(hào)：文件日期：修訂次數(shù)：第1.0次更改批準(zhǔn)審核制定方案設(shè)計(jì)，管理制度例2-1從某單位1999年的職工體檢資料中獲得101名正常成年女子的血清總膽固醇（）的測量結(jié)果如下，試編制頻數(shù)分布表。2.354.213.325.384.263.584.344.844.414.783.953.923.583.664.283.263.502.704.614.752.913.914.594.192.684.524.913.183.684.833.873.953.914.154.554.803.414.123.955.084.533.923.585.353.843.603.514.063.073.554.233.574.833.523.844.503.964.503.274.523.194.593.753.984.134.263.633.875.713.304.784.573.803.933.783.994.484.284.065.265.253.985.033.513.863.023.704.333.264.953.003.26例題2-1(EX2-1.dta):.sumxVariable|ObsMeanStd.Dev.MinMax-------------+-----------------------------------------------------x|1014.029505.65921832.355.71.dir(max)-r(min)3.3600001.gengroup=int((x-2.30)/0.30)*0.30+2.3.tabgroupgroup|Freq.PercentCum.------------+-----------------------------------2.3|10.990.992.6|32.973.962.9|65.949.903.2|87.9217.823.5|1817.8235.643.8|1918.8154.464.1|1716.8371.294.4|1211.8883.174.7|98.9192.085|54.9597.035.3|21.9899.015.6|10.99100.00------------+-----------------------------------Total|101100.00用直接法計(jì)算例2-1某單位名正常成年女子的血清總膽固醇的均數(shù)例2-3第2、3題了解即可，可以用最簡單的方法求出：比如su，tabstat等例2-4某地5例微絲蚴血癥患者治療7年后用間接熒光抗體試驗(yàn)測得其抗體滴度倒數(shù)分別為，求幾何均數(shù)。例題2-4(EX2-4.dta):.meansxVariable|TypeObsMean[95%Conf.Interval]-------------+----------------------------------------------------------x|Arithmetic554-21.32307129.3231|Geometric534.822029.715194124.8121|Harmonic524.24242..------------------------------------------------------------------------Missingvaluesinconfidenceinterval(s)forharmonicmeanindicatethatconfidenceintervalisundefinedforcorrespondingvariable(s).ConsultReferenceManualfordetails.例2-569例類風(fēng)濕關(guān)節(jié)炎（RA）患者血清EBV-VCA-lgG抗體滴度的分布見表2-5第(1)、(2)欄,求其平均抗體滴度。表2-569例RA患者血清EBV-VCA-lgG抗體測定結(jié)果抗體滴度人數(shù)滴度倒數(shù)⑴⑵⑶⑷⑸1:101:201:401:801:1601:3201:6401:128043101011151421020408016032064012801.00001.30101.60211.90312.20412.50512.80623.10724.00003.903016.021019.031024.245137.576539.28686.2144合計(jì)69——150.2778例題2-5(EX2-5.dta):.meansx[fw=f]Variable|TypeObsMean[95%Conf.Interval]-------------+----------------------------------------------------------x|Arithmetic69280.8696212.754348.9851|Geometric69150.6411110.9425204.545|Harmonic6964.8458147.14289103.8391------------------------------------------------------------------------7名病人患某病的潛伏期分別為天，求其中位數(shù)。例題2-6(EX2-6.dta):.centilex--Binom.Interp.--Variable|ObsPercentileCentile[95%Conf.Interval]-------------+-------------------------------------------------------------x|75052.31428613.8例2-78名患者食物中毒的潛伏期分別為小時(shí)，求其中位數(shù)。例題2-7(EX2-7.dta):.centilex--Binom.Interp.--Variable|ObsPercentileCentile[95%Conf.Interval]-------------+-------------------------------------------------------------x|85041.67517.925例2-8試計(jì)算表2-2某醫(yī)院1123名產(chǎn)后出血孕婦人工流產(chǎn)次數(shù)的中位數(shù)。表2-2某醫(yī)院1123名產(chǎn)后出血孕婦人流次數(shù)的分布人流次數(shù)產(chǎn)后出血人數(shù)累計(jì)頻數(shù)累計(jì)頻率（%）(1)(2)(3)(4)040240235.801330=SUM(ABOVE)73265.182232=SUM(ABOVE)96485.843118=SUM(ABOVE)108296.35427=SUM(ABOVE)110998.75511=SUM(ABOVE)112099.7363=SUM(ABOVE)1123100.00合計(jì)=SUM(ABOVE)1123——例題2-8(EX2-8.dta):.tabx[fw=f]x|Freq.PercentCum.------------+-----------------------------------0|40235.8035.801|33029.3965.182|23220.6685.843|11810.5196.354|272.4098.755|110.9899.736|30.27100.00------------+-----------------------------------Total|1123100.00.expandf(1116observationscreated).centilex--Binom.Interp.--Variable|ObsPercentileCentile[95%Conf.Interval]-------------+-------------------------------------------------------------x|112350111例2-10某地118名鏈球菌咽喉炎患者的潛伏期頻數(shù)表見表2-5第(1)、(2)欄，試分別求中位數(shù)及第、第百分位數(shù)。表2-5118名鏈球菌咽喉炎患者的潛伏期天數(shù)人數(shù)，累計(jì)頻數(shù)累計(jì)頻率（%）(1)(2)(3)(4)12～443.424～172117.836～325344.948～247765.360～189580.572～1210790.784～511294.996～411698.3≥1082118100.0例題2-10(EX2-10.dta):.tabx[fw=f]x|Freq.PercentCum.------------+-----------------------------------12|43.393.3924|1714.4117.8036|3227.1244.9248|2420.3465.2560|1815.2580.5172|1210.1790.6884|54.2494.9296|43.3998.31108|21.69100.00------------+-----------------------------------Total|118100.00例2-11試計(jì)算下面三組同齡男孩的身高均數(shù)和極差。甲組：，；乙組：，；丙組：，。例2-13續(xù)例2-11，計(jì)算三組資料的標(biāo)準(zhǔn)差。例題2-11、2-13(EX2-11.dta):.sumx1-x3Variable|ObsMeanStd.Dev.MinMax-------------+-----------------------------------------------------x1|51007.90569490110x2|51003.16227896104x3|51002.91547696104例2-12續(xù)例2-10。已知=，=，計(jì)算名鏈球菌咽喉炎患者潛伏期的四分位數(shù)間距。例題2-12(EX2-10.dta):Tabstatx[fw=f],st(iqr)直接求出四分位間距或者Tabstatx[fw=f],st(q)求出p25p50p75例2-15對(duì)例2-1，已計(jì)算出名正常成年女子的血清總膽固醇均數(shù)，標(biāo)準(zhǔn)差。試估計(jì)該單位：①正常女子血清總膽固醇在以下者占正常女子總?cè)藬?shù)的百分比；②在4.00~5.00之間者占正常女子總?cè)藬?shù)的百分比；③在以上者各占正常女子總?cè)藬?shù)的百分比。例題2-15(EX2-1.dta):.sumxVariable|ObsMeanStd.Dev.MinMax-------------+-----------------------------------------------------x|1014.029505.65921832.355.71recodex(min/4=1)(4.01/5=2)(5.01/max=3),gen(group)tabgroup同時(shí)求出三個(gè)比例由例2-1資料估計(jì)正常女子血清總膽固醇的95%的參考值范圍例題2-16(EX2-1.dta):.sumxVariable|ObsMeanStd.Dev.MinMax-------------+-----------------------------------------------------x|1014.029505.65921832.355.71.dir(mean)-1.96*r(sd)2.7374371.dir(mean)+.96*r(sd)4.6623546例3-1若某市1999年18歲男生身高服從均數(shù)為167.7cm，標(biāo)準(zhǔn)差為5.3cm的正態(tài)分布。從該正態(tài)分布N(167.7,5.32)cm總體中隨機(jī)抽樣100次即共抽取樣本g=100個(gè)，，每次樣本含量=10人，得到每個(gè)樣本均數(shù)及標(biāo)準(zhǔn)差167.41,2.74167.41,2.74165.56,6.57168.20,5.36nj=10=16=5.x1,x2,x3,xi,100個(gè)表3-1N(167.7,5.32)總體中100個(gè)隨機(jī)樣本的、和95%CL(nj=10)樣本號(hào)95%CL樣本號(hào)95%CL1167.412.74165.45169.3751168.473.91165.67171.272165.566.57160.86170.2652165.953.76163.26168.643168.205.36164.37172.0353168.875.77164.74173.004166.674.81163.24170.11*54169.532.07168.05171.005164.895.41161.02168.7655166.105.58162.11170.106166.364.50163.14169.5856167.204.56163.94170.477166.164.04163.27169.0557170.507.66165.02175.988169.115.71165.02173.1958166.444.93162.91169.979167.178.26161.27173.0859168.684.52165.45171.9110166.135.24162.38169.8760168.406.95163.43173.3711167.716.42163.12172.3161171.216.30166.70175.7212168.685.93164.44172.9262170.334.34167.23173.4413166.833.69164.19169.4763169.037.38163.75174.3114169.624.81166.18173.0664167.634.58164.36170.9015166.953.64164.35169.5565168.663.33166.27171.0416170.294.91166.78173.8066168.842.78166.85170.8317169.205.72165.11173.3067169.315.31165.51173.1118167.652.79165.65169.6568168.464.81165.02171.9019166.515.39162.65170.3669168.605.48164.68172.52*20163.283.19161.00165.5770168.475.05164.86172.0921166.294.95162.75169.8471165.685.19161.97169.4022167.655.27163.88171.4272165.688.22159.80171.5623167.644.61164.35170.9473168.034.89164.53171.5324172.617.74167.07178.1574169.375.00165.79172.9425166.654.12163.70169.5975169.168.36163.18175.1426165.194.41162.04168.34*76171.274.99167.71174.8427168.807.68163.31174.3077168.364.50165.14171.5828167.992.58166.14169.8378168.503.55165.96171.0429168.413.43165.95170.8679168.085.33164.27171.9030167.757.53162.36173.1380165.514.71162.14168.88*31164.254.30161.17167.3381167.593.73164.93170.2632166.425.19162.71170.13*82171.124.40167.98174.2733166.904.41163.74170.0583165.925.11162.26169.5834166.774.34163.66169.8884167.864.44164.69171.0435165.775.34161.95169.5985167.436.15163.03171.8336164.126.63159.38168.8686167.906.13163.51172.2837169.834.20166.82172.8487167.596.33163.06172.1238165.164.01162.29168.0288167.744.60164.45171.0339166.596.20162.15171.0389167.408.27161.49173.3240165.653.56163.10168.2090167.186.00162.89171.4841165.724.17162.74168.7191166.433.87163.66169.2142166.227.44160.90171.5492166.624.08163.70169.5443167.716.12163.33172.0993166.304.84162.83169.7644167.255.24163.50170.9994169.705.26165.94173.4545165.695.91161.46169.9295169.176.32164.65173.6946169.065.65165.03173.1096167.896.07163.54172.2347168.766.14164.36173.1597167.486.03163.16171.7948168.644.54165.39171.8998169.934.80166.50173.3749167.723.82164.99170.4599169.405.57165.42173.3950170.394.15167.42173.35100165.695.09162.06169.33*表示該樣本資料算得的可信區(qū)間未包含已知總體均數(shù)167.7cm例題3-1:.drop_all.setseed050322.setobs10obswas0,now10.quietlyfornum1/100:genvarX=invnorm(uniform())*5.3+167.7.formatvar*%9.2f.civar*Variable|ObsMeanStd.Err.[95%Conf.Interval]-------------+-------------------------------------------------------------var1|10167.231.53163.78170.69var2|10164.701.97160.24169.17var3|10165.391.67161.61169.16var4|10168.492.12163.70173.27var5|10169.381.37166.28172.48var6|10166.841.66163.07170.60var7|10167.511.21164.79170.24var8|10167.091.84162.93171.24var9|10167.061.64163.36170.77var10|10167.211.82163.11171.32var11|10167.011.85162.84171.18var12|10167.191.99162.67171.70var13|10168.041.76164.07172.02var14|10168.681.28165.80171.57var15|10167.121.95162.72171.52var16|10168.291.52164.86171.72var17|10165.972.11161.19170.75var18|10164.301.72160.42168.18var19|10168.970.92166.89171.05var20|10167.531.31164.57170.49var21|10165.981.21163.24168.71var22|10166.991.77162.98170.99var23|10166.981.25164.15169.80var24|10167.641.86163.43171.85var25|10163.261.03160.93165.59var26|10167.961.17165.30170.61var27|10166.202.64160.23172.17var28|10168.231.62164.57171.89var29|10167.101.81163.00171.21var30|10165.991.76162.01169.97var31|10169.322.59163.46175.17var32|10168.701.84164.54172.85var33|10165.801.18163.14168.47var34|10169.071.12166.55171.60var35|10166.591.65162.87170.32var36|10165.322.35160.01170.63var37|10169.291.36166.22172.36var38|10167.591.15164.99170.18var39|10167.711.79163.65171.77var40|10169.702.06165.05174.36var41|10167.521.90163.23171.82var42|10166.111.74162.16170.05var43|10166.451.48163.09169.80var44|10168.090.98165.87170.30var45|10167.141.46163.85170.43var46|10169.691.63165.99173.38var47|10165.671.55162.17169.18var48|10165.291.99160.79169.78var49|10167.991.88163.73172.24var50|10167.582.18162.65172.51var51|10165.191.44161.93168.45var52|10169.191.51165.76172.62var53|10168.371.66164.62172.12var54|10167.131.75163.16171.10var55|10167.011.72163.12170.90var56|10166.021.89161.74170.30var57|10169.411.89165.13173.69var58|10169.132.55163.35174.90var59|10165.511.41162.32168.70var60|10165.712.17160.81170.61var61|10167.461.62163.80171.12var62|10168.411.70164.56172.27var63|10168.061.98163.59172.54var64|10167.632.38162.25173.00var65|10168.222.38162.83173.61var66|10171.201.69167.39175.02var67|10166.511.61162.88170.14var68|10169.311.31166.34172.29var69|10164.971.53161.52168.42var70|10169.081.44165.82172.35var71|10168.692.03164.10173.28var72|10168.441.72164.54172.34var73|10167.772.15162.91172.64var74|10171.811.07169.38174.24var75|10168.291.37165.20171.38var76|10166.581.83162.44170.72var77|10169.600.97167.42171.79var78|10167.821.59164.23171.41var79|10166.571.97162.12171.02var80|10166.031.54162.55169.51var81|10167.851.36164.77170.93var82|10167.951.23165.17170.73var83|10169.401.20166.68172.13var84|10170.531.59166.93174.14var85|10170.451.32167.48173.43var86|10167.092.34161.79172.39var87|10166.031.70162.19169.87var88|10168.891.41165.70172.09var89|10169.311.86165.11173.50var90|10168.251.62164.59171.91var91|10166.201.20163.48168.93var92|10167.001.95162.58171.42var93|10168.281.60164.65171.90var94|10170.931.87166.70175.15var95|10163.680.87161.70165.65var96|10165.291.38162.17168.42var97|10169.601.64165.88173.32var98|10170.401.73166.48174.31var99|10166.902.03162.31171.50var100|10168.601.56165.06172.14.xpose,clear.egenmean=rmean(v1-v10).summeanVariable|ObsMeanStd.Dev.MinMax-------------+-----------------------------------------------------mean|100167.58691.628082163.259171.808.di5.3/sqrt(10)1.6760072.histogrammean,bin(9)xlab(163(1)172)ylabfreqgap(4)title("樣本均數(shù)的抽樣分布圖")某地抽得正常成人200名，測得其血清膽固醇的均數(shù)為3.64mmol/L，標(biāo)準(zhǔn)差為1.20mmol/L，試估計(jì)該地正常成人血清膽固醇均數(shù)的95%可信區(qū)間。例題3-3:.cii2003.641.20Variable|ObsMeanStd.Err.[95%Conf.Interval]-------------+-------------------------------------------------------------|2003.64.08485283.4726743.807326為了解甲氨蝶呤(MTX)對(duì)外周血IL-2水平的影響，某醫(yī)生將61名哮喘患者隨機(jī)分為兩組。其中對(duì)照組29例()，采用安慰劑；試驗(yàn)組32例()，采用小劑量甲氨蝶呤(MTX)進(jìn)行治療。測得對(duì)照組治療前IL-2的均數(shù)為20.10IU/ml()，標(biāo)準(zhǔn)差為7.02IU/ml()；試驗(yàn)組治療前IL-2的均數(shù)為16.89IU/ml()，標(biāo)準(zhǔn)差為8.46IU/ml()。問兩組治療前基線的IL-2總體均例題3-4:.ttesti2920.107.023216.898.46Two-samplettestwithequalvariances------------------------------------------------------------------------------|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x|2920.11.3035817.0217.4297322.77027y|3216.891.4955318.4613.8398419.94016---------+--------------------------------------------------------------------combined|6118.416071.0129397.91130916.3898920.44225---------+--------------------------------------------------------------------diff|3.212.002304-.79660047.2166------------------------------------------------------------------------------Degreesoffreedom:59Ho:mean(x)-mean(y)=diff=0Ha:diff<0Ha:diff~=0Ha:diff>0t=1.6032t=1.6032t=1.6032P<t=0.9429P>|t|=0.1142P>t=0.0571數(shù)相差有多大？

例3-5某醫(yī)生測量了36名從事鉛作業(yè)男性工人的血紅蛋白含量，算得其均數(shù)為130.83g/L，標(biāo)準(zhǔn)差為25.74g/L。問從事鉛作業(yè)工人的血紅蛋白是否不同于正常成年男性平均值140g/L？

例題3-5(EX3-5.dta):.ttestx=140One-samplettest------------------------------------------------------------------------------Variable|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x|36130.83334.2901725.74102122.1238139.5428------------------------------------------------------------------------------Degreesoffreedom:35Ho:mean(x)=140Ha:mean<140Ha:mean~=140Hat=-2.1367t=-2.1367t=-2.1367P<t=0.0198P>|t|=0.0397P>t=0.9802.ttesti36130.833325.74102140One-samplettest------------------------------------------------------------------------------|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x|36130.83334.2901725.74102122.1238139.5428------------------------------------------------------------------------------Degreesoffreedom:35Ho:mean(x)=140Ha:mean<140Ha:mean~=140Ha:mean>140t=-2.1367t=-2.1367t=-2.1367P<t=0.0198P>|t|=0.0397P>t=0.9802例3-6為比較兩種方法對(duì)乳酸飲料中脂肪含量測定結(jié)果是否不同，隨機(jī)抽取了10份乳酸飲料制品，分別用脂肪酸水解法和哥特里－羅紫法測定其結(jié)果如表3-5第(1)~(3)欄。問兩法測定結(jié)果是否不同？

表3-5兩種方法對(duì)乳酸飲料中脂肪含量的測定結(jié)果(%)編號(hào)(1)哥特里－羅紫法(2)脂肪酸水解法(3)差值d(4)=(2)(3)10.8400.580=b2-c2\#"0.000"0.26020.5910.509=b3-c3\#"0.000"0.08230.6740.500=b4-c4\#"0.000"0.17440.6320.316=b5-c5\#"0.000"0.31650.6870.337=b6-c6\#"0.000"0.35060.9780.517=b7-c7\#"0.000"0.46170.7500.454=b8-c8\#"0.000"0.29680.7300.512=b9-c9\#"0.000"0.21891.2000.997=b10-c10\#"0.000"0.203100.8700.506=b11-c11\#"0.000"0.364=sum(d2:d11\#"0.000")2.724例題3-6(EX3-6.dta):.ttestx1=x2Pairedttest------------------------------------------------------------------------------Variable|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x1|10.7952.0583003.1843618.6633155.9270845x2|10.5228.0588125.1859814.389757.655843---------+--------------------------------------------------------------------diff|10.2724.034368.1086812.1946542.3501458------------------------------------------------------------------------------Ho:mean(x1-x2)=mean(diff)=0Ha:mean(diff)<0Ha:mean(diff)~=0Ha:mean(diff)>0t=7.9260t=7.9260t=7.9260P<t=1.0000P>|t|=0.0000P>t=0.0000例3-7為研究國產(chǎn)四類新藥阿卡波糖膠囊的降血糖效果，某醫(yī)院用40名2型糖尿病病人進(jìn)行同期隨機(jī)對(duì)照試驗(yàn)。試驗(yàn)者將這些病人隨機(jī)等分到試驗(yàn)組(用阿卡波糖膠囊)和對(duì)照組(用拜糖平膠囊)，分別測得試驗(yàn)開始前和8周后的空腹血糖，算得空腹血糖下降值見表3-6，能否認(rèn)為該國產(chǎn)四類新藥阿卡波糖膠囊與拜糖平膠囊對(duì)空腹血糖的降糖效果不同？

表3-6試驗(yàn)組和對(duì)照組空腹血糖下降值(mmol/L)試驗(yàn)組X1(n1=20)-0.70-5.602.002.800.703.504.005.807.10-0.502.50-1.601.703.000.404.504.602.506.00-1.40對(duì)照組X2(n2=20)3.706.505.005.200.800.200.603.406.60-1.106.003.802.001.602.0001.70-2.00例題3-7(EX3-7.dta):.ttestx,by(group)Two-samplettestwithequalvariances------------------------------------------------------------------------------Group|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------1|202.065.68426973.060147.63280713.4971932|202.625.541242.4204991.4921723.757828---------+--------------------------------------------------------------------combined|402.345.43292312.7380461.469333.22067---------+--------------------------------------------------------------------diff|-.56.8724482-2.3261791.206179------------------------------------------------------------------------------Degreesoffreedom:38Ho:mean(1)-mean(2)=diff=0Ha:diff<0Ha:diff~=0Ha:diff>0t=-0.6419t=-0.6419t=-0.6419P<t=0.2624P>|t|=0.5248P>t=0.7376例3-8在上述例3-7國產(chǎn)四類新藥阿卡波糖膠囊的降血糖效果研究中，測得用拜糖平膠囊的對(duì)照組20例病人和用阿卡波糖膠囊的試驗(yàn)組20例病人，其8周時(shí)糖化血紅蛋白HbA1c(%)下降值如表3-7。問用兩種不同藥物的病人其HbA1表3-7對(duì)照組和試驗(yàn)組HbA1c分組n對(duì)照組201.461.36試驗(yàn)組201.130.70例題3-8:.ttesti201.461.36201.130.70,uneTwo-samplettestwithunequalvariances------------------------------------------------------------------------------|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x|201.46.30410521.36.82350042.0965y|201.13.1565248.7.80238991.45761---------+--------------------------------------------------------------------combined|401.295.17086021.080615.94940261.640597---------+--------------------------------------------------------------------diff|.33.3420234-.37015141.030151------------------------------------------------------------------------------Satterthwaite'sdegreesoffreedom:28.4068Ho:mean(x)-mean(y)=diff=0Ha:diff<0Ha:diff~=0Hat=0.9648t=0.9648t=0.9648P<t=0.8286P>|t|=0.3428P>t=0.1714.ttesti201.461.36201.130.70,unewTwo-samplettestwithunequalvariances------------------------------------------------------------------------------|ObsMeanStd.Err.Std.Dev.[95%Conf.Interval]---------+--------------------------------------------------------------------x|201.46.30410521.36.82350042.0965y|201.13.1565248.7.80238991.45761---------+--------------------------------------------------------------------combined|401.295.17086021.080615.94940261.640597---------+--------------------------------------------------------------------diff|.33.3420234-.36910621.029106------------------------------------------------------------------------------Welch'sdegreesoffreedom:29.397Ho:mean(x)-mean(y)=diff=0Ha:diff<0Ha:diff~=0Ha:diff>0t=0.9648t=0.9648t=0.9648P<t=0.8288P>|t|=0.3425P>t=0.1712.例3-9試用矩法對(duì)表3-1中計(jì)算機(jī)模擬抽樣所得100個(gè)樣本均數(shù)進(jìn)行正態(tài)性檢驗(yàn)(數(shù)據(jù)見前表3-1)。例題3-9:.drop_all.setseed050322.setobs10obswas0,now10.quietlyfornum1/100:genvarX=invnorm(