DNA-Chip Analyzer (dChip) is a software package (developed by Dr. Cheng Li) implementing model-based expression analysis of oligonucleotide arrays and several high-level analysis procedures. The model-based approach allows probe-level analysis on multiple arrays. By pooling information across multiple arrays, it is possible to assess standard errors for the expression indexes. This approach also allows automatic probe selection in the analysis stage to reduce errors due to cross-hybridizing probes and image contamination. High-level analysis in dChip includes comparative analysis and hierarchical clustering.