SPSS Missing Value Analysis 7.5

SPSS is a powerful software package for data management and analysis. The Missing Value Analysis option extends this power by giving you tools for discovering patterns of missing data that occur frequently in survey and other types of data and for dealing with data that contains missing values. Often in survey data, patterns become evident that will affect analysis. For example, you might find that people living in certain areas are reluctant to give their annual incomes, thus creating missing values in your data. If you leave these values out, are your statistical conclusions valid? Another concern is that the statistical algorithms being used make valid assumptions about the data distribution. [via]

http://www.sscnet.ucla.edu/labs/SPSS13/SPSSMi...