If the product is really useless, this would on average produce one study showing the product was beneficial, one study showing it was harmful and thirty-eight inconclusive studies (38 is 95% of 40).
如果該產品真的是無用的，這個數據便會是由1份指出產品是好的、1份指出產品是不好的及38份不確定的研究(38是40的95%)得出的平均值。