In all instances, after taking the log2, groups of probes that have not hybridized to anything should be normally distributed and have mean zero. We can therefore split the probes into groups and perform a t-test for each one. DetectiV does this using the do.t.test function. The normalized (or raw) data are split into groups as defined by the unique values of a user defined annotation column. Providing each group has more than two probes, a t-test is performed to test the difference of the observations from zero. The average value is also calculated. The output is a table, sorted by p value.