st: curious problem with 2 sample smirnov test

[Anjanette Chan Tack <amc75@uchicago.edu>]

Hi -

I am running a 2 sample smirnov test that tests for equality of distributions on an outcome for white and non-white majority neighborhoods at 5 different poverty levels. The test works smoothly for all but one poverty level, at which point, I get an error message saying: "majw7 takes on 0 values, not 2". When I click for more info, it says:

"Return code 450 __________ is not a 0/1 variable;      number of successes invalid; p invalid; __________ takes on __________ values, not 2; You have used a command, such as bitest, that requires the variable take on only the values 0, 1, or missing, but the variable you specified does not meet that restriction.  (You can also get this message from, for example, bitesti, when you specify a number of successes greater than the number of observations or a probability not between 0 and 1.)"

What is curious about this message is that it rejects my group variable "majw7" as a 0/1 variable at this poverty level, although it had no problem with "majw7" at the other poverty levels. If someone can suggest what might be going on and how I can work around this, I'd be grateful. For more info, see below:

Example of commands that worked:
ksmirnov LgAllSt7 if povrat7 >= 80 & povrat7 <= 100, by(majw7)

The command that did not work:
ksmirnov LgAllSt0 if povrat0 >= 0 & povrat0 < 20, by(majw0)

I am wondering if the problem may be the limited number of cases I have at this poverty level. The crosstabs below show the distribution of neighborhoods (white majority = 1, and non-white majority = 0) across different poverty levels (e.g. 20 means 0 to 20%, etc)


 poverty |
    rate,5 |
   ordinal | White maj neighb = 1
    groups |         0          1 |     Total
-----------+----------------------+----------
        20 |       154        467 |       621 
        40 |       154         26 |       180 
        60 |        37          3 |        40 
        80 |         3          1 |         4 
-----------+----------------------+----------
     Total |       348        497 |       845 


Thank you for your advice.

Sincerely
AM. Chan Tack
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