Revista Panamericana de Salud Pública
On-line version ISSN 1680-5348
Print version ISSN 1020-4989
IRALA, Jokin de; FERNANDEZ-CREHUET NAVAJAS, Rafael and SERRANO DEL CASTILLO, Amparo. Abnormally broad confidence intervals in logistic regression: interpretation of results from statistical programs. Rev Panam Salud Publica [online]. 1997, vol.1, n.3, pp.230-234. ISSN 1680-5348. http://dx.doi.org/10.1590/S1020-49891997000300010.
This study describes the behavior of eight statistical programs (BMDP, EGRET, JMP, SAS, SPSS, STATA, STATISTIX, and SYSTAT) when performing a logistic regression with a simulated data set that contains a numerical problem created by the presence of a cell value equal to zero. The programs respond in different ways to this problem. Most of them give a warning, although many simultaneously present incorrect results, among which are confidence intervals that tend toward infinity. Such results can mislead the user. Various guidelines are offered for detecting these problems in actual analyses, and users are reminded of the importance of critical interpretation of the results of statistical programs.