This is an email to the folk at EpiData.

In my examples below I'm using the data file bromar.rec, one of the example data files that come with EpiData.

The variable km has some missing data (.). This data seems to be correctly treated as missing values for some commands but not for all. One example is the StatTables command. Below is an example of the command I typed into EpiData and the resulting output: . StatTables sex /idr=km SEX N NKM P10KM P90KM Female 490 423 42.00 . Male 3537 3197 32.00 .

As you can see the missing values are included in the calculation for the 90th percentile. It's obviously a bug. However you may not detect the bug if you're interested in the interquartile range: . StatTables sex /iqr=km SEX N NKM P25KM P75KM Female 490 423 67.00 265.00 Male 3537 3197 42.00 265.00 If you do a "describe" you can see that 265 is definitely not the 75th percentile.

Suzanna Vidmar Senior Research Officer

Clinical Epidemiology and Biostatistics Unit Royal Children's Hospital Flemington Rd Parkville Victoria 3052

telephone: +61 3 9345 6372 facsimile: +61 3 9345 6000