Hi,
I would like to estimate a confidence interval for a proportion when there are zero counts. I find that -ci prop- will give a CI estimate, while the -proportion- estimate command never does, and I wondered why. Perhaps I missed it but the manual suggests that both commands estimate the SE/confidence intervals in similar ways.

Code:
set obs 100
gen x=  _n>50
gen y= _n >75
tab x y
proportion y, over(x) citype(wilson)
/*

Proportion estimation             Number of obs   =        100

--------------------------------------------------------------
             |                                   Wilson
             | Proportion   Std. Err.     [95% Conf. Interval]
-------------+------------------------------------------------
         y@x |
        0 0  |          1          0             .           .
        0 1  |         .5   .0707107      .3664451    .6335549
        1 0  |          0  (no observations)
        1 1  |         .5   .0707107      .3664451    .6335549
--------------------------------------------------------------

*/

ci prop y if x==0, wilson

/*
                                                         ------ Wilson ------
    Variable |        Obs  Proportion    Std. Err.       [95% Conf. Interval]
-------------+---------------------------------------------------------------
           y |         50           0           0        6.94e-18    .0713476

*/


ci prop x if y==1, wilson
/*
                                                         ------ Wilson ------
    Variable |        Obs  Proportion    Std. Err.       [95% Conf. Interval]
-------------+---------------------------------------------------------------
           x |         25           1           0        .8668077           1
*/

Thanks,
Scott