. 
. capture program drop muratio



. program define muratio, rclass
  1.            version 11
  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') nodots ///
> saving(771bs2_9,replace): muratio p_dom p_for



Warning:  Because 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 that 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 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