Why is the Chronos dependency score smaller than -1?

If you’re interested in making a binary call on whether a gene is essential or not, you probably should use the “Probability of gene dependency” instead of “Gene Effect”.

See the the guidance at DepMap Genetic Dependencies FAQ for more explanation. (It was written when the method we used to compute “Gene Effect” was CERES and although we now use a newer method, Chronos, the advice given is still valid.)