为什么logistic回归结果中提出了一个样本 stata

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我一共997个数据   可用stata做logistic回归后，结果显示数据只有996，怎么回事呢？ Number of obs   =        996
                                                  LR chi2(12)     =      38.84

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关键词：logistic回归 logistic ogistic logisti logist 样本

只看结果很难知道什么原因
软件不会出错

蓝色 发表于 2015-10-9 18:08
只看结果很难知道什么原因
软件不会出错

我看一篇博士论文  他观测值126，可logistic结果中number of obs是122，是什么原因呢 ？谢谢了

我猜不出来

蓝色 发表于 2015-10-9 18:59
我猜不出来

可能有missing data

蓝色 发表于 2015-10-9 18:59
我猜不出来

可能有missing data

andruw 发表于 2015-10-9 19:35
可能有missing data

这样结果可以用吗？我看其他论文也有这种情况

蓝色 发表于 2015-10-9 18:59
我猜不出来

亲 我问一下Hosmer-Lemeshow拟合度检验的命令是什么啊？我没找到

Title

    [R] logit postestimation -- Postestimation tools for logit


Description

    The following postestimation commands are of special interest after logit:

    Command               Description
    ---------------------------------------------------------------------------------------
    estat classification  report various summary statistics, including the classification
                            table
    estat gof             Pearson or Hosmer-Lemeshow goodness-of-fit test

Title

    [R] estat gof -- Pearson or Hosmer-Lemeshow goodness-of-fit test


Syntax

        estat gof [if] [in] [weight] [, options]

    gof_options           Description
    ---------------------------------------------------------------------------------------
    Main
      group(#)            perform Hosmer-Lemeshow goodness-of-fit test using # quantiles
      all                 execute test for all observations in the data
      outsample           adjust degrees of freedom for samples outside estimation sample
      table               display table of groups used for test
    ---------------------------------------------------------------------------------------
    fweights are allowed; see weight.
    estat gof is not appropriate after the svy prefix.


Menu for estat

    Statistics > Postestimation > Reports and statistics


Description

    estat gof reports the Pearson goodness-of-fit test or the Hosmer-Lemeshow
    goodness-of-fit test.

    estat gof requires that the current estimation results be from logistic, logit, or
    probit.  For estat gof after poisson, see [R] poisson postestimation.  For estat gof
    after sem, see [SEM] estat gof.


Options

        +------+
    ----+ Main +---------------------------------------------------------------------------

    group(#) specifies the number of quantiles to be used to group the data for the
        Hosmer-Lemeshow goodness-of-fit test.  group(10) is typically specified.  If this
        option is not given, the Pearson goodness-of-fit test is computed using the
        covariate patterns in the data as groups.

    all requests that the statistic be computed for all observations in the data, ignoring
        any if or in restrictions specified by the estimation command.

    outsample adjusts the degrees of freedom for the Pearson and Hosmer-Lemeshow
        goodness-of-fit tests for samples outside the estimation sample.  See Samples other
        than the estimation sample in [R] estat gof.

    table displays a table of the groups used for the Hosmer-Lemeshow or Pearson
        goodness-of-fit test with predicted probabilities, observed and expected counts for
        both outcomes, and totals for each group.


Examples

    Setup
        . webuse lbw

    Fit logistic regression to predict low birth weight
        . logistic low age lwt i.race smoke ptl ht ui

    Perform goodness-of-fit test
        . estat gof

    Same as above, but use 10 quantiles
        . estat gof, group(10)

    Same as above, but display table of groups used for test
        . estat gof, group(10) table


Stored results

    estat gof stores the following in r():

    Scalars   
      r(N)                number of observations
      r(m)                number of covariate patterns or groups
      r(df)               degrees of freedom
      r(chi2)             chi-squared