I agree that there are some things they could have done wrong that aren't explicitly ruled out in http://www.atheistberlin.com/study http://www.atheistberlin.co

I agree that there are some things they could have done wrong that aren't explicitly ruled out in http://www.atheistberlin.com/study http://www.atheistberlin.com/study: Were the packages the same weight or were some of them heavier? Were the packages given over to the same post office, or were some packages given to one office and some to another? What order were the packages handed over to the post office? Assuming that there were no errors like that, this does appear to be a well designed experiment, and they are using rigorous statistical methods that are appropriate to carry out the tests, so it is entirely valid to draw causal inference that packages of that weight delivered on that day to that post office were caused to be delivered later if they had the atheist tape on them. It would be hard to generalise that more to say that every package delivered from anywhere to the US on any day will be delayed. It is also not necessarily possible to jump from the valid causal inference above to "USPS employs bigots" without further experimentation - perhaps the difference occurred before the packages reached USPS? Perhaps USPS employees occasionally have to make a judgement call about the last packages to go into a crate, and they are more likely to put in a package that might be time sensitive than one with tape that implies it probably isn't (it would be interesting to see the impact of other labelled tapes, like Christian, Muslim, Toys, Business Documents, Baby Formula, Shoes and so on).