Methods for addressing missing data in psychiatric and developmental research.
OBJECTIVE
First, to provide information about best practices in handling missing data so that readers can judge the quality of research studies. Second, to provide more detailed information about missing data analysis techniques and software on the Journal's Web site at www.jaacap.com.


METHODS
We focus our review of techniques on those that are based on the "Missing at Random" assumption and are either extremely popular because of their convenience or that are harder to employ but yield more precise inferences.


RESULTS
The literature regarding missing data indicates that deletion of observations with missing data can yield biased findings. Other popular methods for handling missing data, notably replacing missing values with means, can lead to confidence intervals that are too narrow as well as false identifications of significant differences (type I statistical errors). Methods such as multiple imputation and direct maximum likelihood estimation are often superior to deleting observations and other popular methods for handling missing data problems.


CONCLUSIONS
Psychiatric and developmental researchers should consider using multiple imputation and direct maximum likelihood estimation rather than deleting observations with missing values.
Croy
Calvin D
CD
National Center for American Indian and Alaska Native Mental Health, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA. calvin.croy@uchsc.edu
Novins
Douglas K
DK
D000293:Adolescent; D000296:Adolescent Psychiatry / Q000706:statistics & numerical data*; D015982:Bias; D002648:Child; D002665:Child Psychiatry / Q000706:statistics & numerical data*; D003625:Data Collection / Q000706:statistics & numerical data; D003627:Data Interpretation, Statistical; D006801:Humans; D008137:Longitudinal Studies; D008432:Mathematical Computing; D015233:Models, Statistical; D015203:Reproducibility of Results; D012107:Research Design / Q000706:statistics & numerical data*