统计描述的Stata实现

..统计描述的Stata实现本章主要用到的Stata主要命令*描述性统计：summary变量名[weight＝],detail频数表:tabulate变量名[weight＝]计算均数：means变量名[weight＝]频数分布图：histogram变量名,bin<>start<>*Stata的命令可以用前几个字母代替,如summary可以由su代替,tabulate可以由tab代替。下面就直接用缩写,不再赘述。例2-1某市1982年调查120名20岁男子的身高〔cm资料如下,试编制频数表和频数图。164.4169.2174.7175.0165.0162.8170.2160.1170.9170.1175.5170.3172.3168.2166.7171.7166.8171.6165.2172.0171.7168.8171.8174.5171.7172.7166.3174.0169.0174.5171.8174.9180.0173.5178.1169.7176.1181.3173.8164.7172.2172.8178.6172.0182.5172.0173.5166.3176.1169.2176.4168.4171.0169.1166.9181.1170.4165.2168.0172.4164.3166.9176.4164.2177.2168.3177.8173.0167.4173.2169.9172.1170.4174.8172.1164.4170.5165.0172.8166.8175.8171.1174.8172.7169.4178.2174.1177.2170.0172.7168.3177.1172.5166.3175.1174.4162.3171.3177.0163.5168.8177.6175.2171.5172.5179.1172.6184.8168.3182.8170.3167.5171.2170.4166.9178.5164.1169.5173.4170.3数据格式如下：x1164.42175.53171.74171.85172.26176.47164.38169.99175.810168.311168.812170.313169.214170.315168.816174.917172.818168.419166.920172.121171.122177.123177.624167.525174.726172.327171.82818029178.63017131176.432170.433174.834172.535175.236171.23717538168.239174.540173.54117242169.143164.244174.845172.746166.347171.548170.44916550166.751171.752178.153182.554166.955177.256172.157169.458175.159172.560166.961162.862171.763172.764169.76517266181.167168.368164.469178.270174.471179.172178.573170.274166.875166.376176.177173.578170.479177.880170.581174.182162.383172.684164.185160.186171.68717488181.389166.390165.2911739216593177.294171.395184.896169.597170.998165.299169100173.8101176.1102168103167.4104172.8105170106177107168.3108173.4109170.1110172111174.5112164.7113169.2114172.4115173.2116166.8117172.7118163.5119182.8120170.3为制作频数表,键入Stata命令：.genf=int<<x-160>/2>*2+160产生用以作频数表的新变量"f".tabf对变量"f"作频数表"gen"命令产生新变量"f",将各观察值转换成相应该组的下限值。int为取整函数,结果为括号内函数值的整数部分,如int<3.24>=3。"160”为第一组的下限,"2”为组距。以第一例观察值160.1cm为例,f=int<<160.1-160结果如下：f|Freq.PercentCum.------------+-----------------------------------160|10.830.83162|32.503.33164|108.3311.67166|119.1720.83168|1613.3334.17170|2218.3352.50172|2218.3370.83174|1411.6782.50176|108.3390.83178|54.1795.00180|32.5097.50182|21.6799.17184|10.83100.00------------+-----------------------------------Total|120100.00histf,start<160>width<2>作频数图结果如下：例2-2某医生测定230名正常成年男子的空腹血清胰岛素样生长因子-1〔IGF-1F水平,整理后编制为频数分布表〔表2-2,请根据该频数分布表作频数图。表2-2230名正常人空腹血清胰岛素样生长因子-1水平中位数的计算IGF-1F〔1人数〔2频率<%><3>累计频数〔4累计频率<%>〔5=〔4/50~3013.043013.0150~7130.8710143.9250~4921.3015065.2350~2812.1717877.4450~146.0919283.5550~125.2220488.7650~104.3521493.0750~83.4822296.5850~52.1722798.7950~105031.30230100.0合计230100.00——Stata数据格式如下：xf150302150713250494350285450146550127650108750898505109503tabx[weight=f]制作汇总表的频数表在本例中,x的取值为各组的下限,而f是各组的频数,所以需要用Stata的频数选项[weight=]。结果：x|Freq.PercentCum.------------+-----------------------------------50|3013.0413.04150|7130.8743.91250|4921.3065.22350|2812.1777.39450|146.0983.48550|125.2288.70650|104.3593.04750|83.4896.52850|52.1798.70950|31.30100.00------------+-----------------------------------Total|230100.00histx[weight=f],start<50>width<100>制作频数图例2-3随机测量某地10名20~30岁健康男性居民血清铁含量〔,测量值分别为6.58,7.42,15.32,15.78,17.60,17.98,15.21,17.53,20.11,22.64,试求其平均血清铁含量。Stata数据为x16.5827.42315.32415.78517.6617.98715.21817.53920.111022.64sux计算均数标准差结果：Variable|ObsMeanStd.Dev.MinMax-------------+--------------------------------------------------------x|1015.6175.0752546.5822.64所以平均平均血清铁含量为15.617。例2-4计算例2-1的频数表〔表2-3中120名男子的平均身高显然,如果用Stata,对于例2-1的资料不需要事先转化为频数表,然后再计算均数。不妨用例2-2作为例子展示Stata计算频数表资料的均数。sux[weight=f]计算频数表资料的均数结果：Variable|ObsWeightMeanStd.Dev.MinMax-------------+-----------------------------------------------------------------x|10230290223.412350950例2-58名麻疹易感儿接种麻疹疫苗3周后,其血凝抑制抗体滴度分别为1:4,1:8,1:16,1:32,1:64,1:128,1:256,1:512。试求其平均抗体滴度。数据格式：x1428316432564612872568512genlogx=log<x>计算x的自然对数sulogx计算自然对数的均数,得到3.81231dispexp<3.81231>计算均数的反对数,即指数得到几何均数为45.254857另外,Stata还有一个直接计算几何均数的命令：meansx结果为：Variable|TypeObsMean[95%Conf.Interval]-------------+----------------------------------------------------------x|Arithmetic8127.5-20.53203275.532|Geometric845.2548310.94481187.1206|Harmonic816.06275..------------------------------------------------------------------------Missingvaluesinconfidenceinterval<s>forharmonicmeanindicatethatconfidenceintervalisundefinedforcorrespondingvariable<s>.ConsultReferenceManualfordetails.Means命令计算算术均数、几何均数以及调和均数,其中几何均数为45.25483,和前面的结果相同。例2-6某地区50名麻疹易感儿童接种麻疹疫苗3周后,测其血凝抑制抗体滴度,如表2-4中第〔1栏和第〔2栏,求平均抗体滴度。表2-450名麻疹易感儿童平均抗体滴度计算表抗体滴度〔1人数〔2滴度倒数〔3〔4〔5=〔2×〔41:4140.60210.60211:8280.90311.80621:166161.20417.22461:3210321.505115.05101:6416641.806228.89921:12881282.107216.85761:25652562.408212.04101:51225122.70935.4186合计50——87.9003数据如下：xf14128231664321056416612887256585122genlogx=log<x>计算x的自然对数sulogx〔weight=f〕计算自然对数的均数,得到4.04798dispexp<4.04798>计算均数的反对数,即指数得到几何均数为57.281631也可以用meansx[weight=f]结果：<analyticweightsassumed>Variable|TypeObsMean[95%Conf.Interval]-------------+----------------------------------------------------------x|Arithmetic895.76-2.30755193.8275|Geometric857.281622.59723145.2029|Harmonic832.82051..------------------------------------------------------------------------Missingvaluesinconfidenceinterval<s>forharmonicmeanindicatethatconfidenceintervalisundefinedforcorrespondingvariable<s>.ConsultReferenceManualfordetails.例2-75名成年男子的体重〔kg为60,70,75,80,90,求中位数。例2-8某医生测定了6名正常成年男子的空腹血清胰岛素样生长因子-1〔IGF- 1F水平为150,170,185,245,265,280,求中位数。注：这两个例子用软件算实在是浪费,可以用sux,detail来处理。对于summary,加上detail后可以输出百分位数,其中的P50就是中位数。x-------------------------------------------------------------PercentilesSmallest1%60605%607010%6075Obs525%7080SumofWgt.550%75Mean75LargestStd.Dev.11.1803475%807090%9075Variance12595%9080Skewness099%9090Kurtosis2.05例2-98名7岁男孩的身高〔cm分别为116,118,119,120,121,123,125,126。请计算这8名7岁男孩身高的第25百分位数和第90百分位数。Stata数据为：x116118119120121123125126Stata命令为：sux,d结果为：x--------------------------------------