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       log:  /Users/baum/doc/Courses 2008-2009/EC771 S2009/771bstrap1.smcl
  log type:  smcl
 opened on:  25 Mar 2009, 22:41:50



. 
. 
. capture program drop muratio



. program define muratio, rclass
  1.            version 10.1
  2.            syntax varlist(min=2 max=2)
  3.            tempname ymu
  4.            summarize `1', meanonly
  5.            scalar `ymu' = r(mean)
  6.            summarize `2', meanonly
  7.            return scalar ratio = `ymu'/r(mean)
  8. end



. 
. set seed 10101



. local reps 1000



. 
. webuse auto, clear
(1978 Automobile Data)



. tabstat price, by(foreign) stat(n mean semean)



Summary for variables: price
     by categories of: foreign (Car type)



 foreign |         N      mean  se(mean)
---------+------------------------------
Domestic |        52  6072.423  429.4911
 Foreign |        22  6384.682  558.9942
---------+------------------------------
   Total |        74  6165.257  342.8719
----------------------------------------



. 
. g p_dom = price if foreign==0
(22 missing values generated)



. g p_for = price if foreign==1
(52 missing values generated)



. 
. muratio p_dom p_for



. return list



scalars:
              r(ratio) =  .9510925132761489



. 
. bootstrap  r(ratio), reps(`reps') saving(771bs2_9,replace): muratio p_dom p_for
(running muratio on estimation sample)



Warning:  Since muratio is not an estimation command or does not set e(sample),
          bootstrap has no way to determine which observations are used in calculating
          the statistics and so assumes that all observations are used.  This means no
          observations will be excluded from the resampling because of missing values
          or other reasons.



          If the assumption is not true, press Break, save the data, and drop the
          observations that are to be excluded.  Be sure that the dataset in memory
          contains only the relevant data.



Bootstrap replications (1000)
----+--- 1 ---+--- 2 ---+--- 3 ---+--- 4 ---+--- 5 
..................................................    50
..................................................   100
..................................................   150
..................................................   200
..................................................   250
..................................................   300
..................................................   350
..................................................   400
..................................................   450
..................................................   500
..................................................   550
..................................................   600
..................................................   650
..................................................   700
..................................................   750
..................................................   800
..................................................   850
..................................................   900
..................................................   950
..................................................  1000



Bootstrap results                               Number of obs      =        74
                                                Replications       =      1000



      command:  muratio p_dom p_for
        _bs_1:  r(ratio)



------------------------------------------------------------------------------
             |   Observed   Bootstrap                         Normal-based
             |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       _bs_1 |   .9510925   .1072875     8.86   0.000     .7408128    1.161372
------------------------------------------------------------------------------



. 
. use 771bs2_9,clear
(bootstrap: muratio)



.  
. histogram _bs_1, normal name(g771bs2_r, replace) xsize(9) ysize(7) ///
>  ti("Bootstrap distribution of ratio of means") 
(bin=29, start=.68787545, width=.02437044)



. 
. qui graph export 771bstrap1.pdf, replace



. 
. 
. log close
       log:  /Users/baum/doc/Courses 2008-2009/EC771 S2009/771bstrap1.smcl
  log type:  smcl
 closed on:  25 Mar 2009, 22:42:00
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