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1、第二章统计描述的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。164.4169.2174.7175.0165.0162.8170.2160.1170.9
2、170.1175.5170.3172.3168.2166.7171.7166.8171.6165.2172.0171.7168.8171.8174.5171.7172.7166.3174.0169.0174.5171.8174.9180.0173.5178.1169.7176.1181.3173.8164.7172.2172.8178.6172.0182.5172.0173.5166.3176.1169.2176.4168.4171.0169.1166.9181.1170.4165.2168.0172.4164.3166.9176.4164.2177.2168.3177.8173.0167.4
3、173.2169.9172.1170.4174.8172.1164.4170.5165.0172.8166.8175.8171.1174.8172.7169.4178.2174.1177.2170.0172.7168.3177.1172.5166.3175.1174.4162.3171.3177.0163.5168.8177.6175.2171.5172.5179.1172.6184.8168.3182.8170.3167.5171.2170.4166.9178.5164.1169.5173.4170.3数据格式如下:x1164.42175.53171.74171.85172.26176.47
4、164.38169.99175.810168.311168.812170.313169.214170.315168.816174.917172.818168.419166.920172.121171.122177.123177.624167.525174.726172.327171.82818029178.63017131176.432170.433174.834172.535175.236171.23717538168.239174.540173.54117242169.143164.244174.845172.746166.347171.548170.44916550166.751171.
5、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.
6、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:.gen f=in t(x-160)/2)*2+160产生用以作频数表的新变量“f ”.tab f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。i
7、nt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)/2)*2+160=160，则它应归入 “160”组。结果如下：f |+-Freq.Perce ntCum160 |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 |54.17
8、95.00180 |32.5097.50182 |21.6799.17184 |10.83100.00+Total |120100.00作频数图hist f,start(160) width(2)结果如下:VTrs neD00O-60-4U-2U-60X56X70X80X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2-2 230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f（2）频率(%)(3)累计频数 f（4）累计频率（%）（5）=（4）/n50
9、3013.043013.01507130.8710143.92504921.3015065.23502812.1717877.4450146.0919283.5550125.2220488.7650104.3521493.075083.4822296.585052.1722798.7950105031.30230100.0合计230100.00Stata数据格式如下：xf150302150713250494350285450146550127650108750898505109503tab x 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 St
10、atahist x weight=f,start(50) width(IOO)的频数选项weight=。结果：x |+Freq.Perce ntCum.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 |230100.00制作频数图3UO.2UO-VPTSDeDO002004O6000800O例2-3 随机测量某
11、地10名2030岁健康男性居民血清铁含量（mo1 /L ）,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x16.5827.42315.32415.78517.6617.98715.21817.53920.111022.64su x计算均数标准差结果：Variable |ObsMea n Std. 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。su x weight=f计算频数表资料的均数结果:Variable | Obs+WeightMea n Std. Dev.MinMaxx |10230290223.412350950例2-5
