My ratio on sexed but not-sexlinked chicks is pretty close to Debid's. But I once got seven pullets on a straight run order of seven buff orps. The odds of that happening are probably similar to you getting 3 out of 10 wrong with a 90% guarantee rate. That math gets a bit complicated though. I'm not working through it.
If you got them from a pullet bin at a feed store, another factor enters. Some feed store employees are good and know what they are doing, but not all. The person unloading them could have easily messed up. Still, you have had unusually rotten luck.
If you got them from a pullet bin at a feed store, another factor enters. Some feed store employees are good and know what they are doing, but not all. The person unloading them could have easily messed up. Still, you have had unusually rotten luck.