The range of ratio which can be used to indicate that a gene was not expressed in the cancerous tissue but was expressed in the healthy tissue is 0.5 - 0.0625.
Microarray is a technique that is used to measure the differences between the cancer cells and the normal cells. The method measures the amount of mRNA for genes that are present in a sample and compare the results between healthy and cancerous cells. A value of less than 1 indicates that the genes from the microarray are more active in normal cells.