By May 1916 they were still corresponding in a friendly manner. However Pearson misunderstood the assumptions of Fisher 's maximum likelihood method, and criticised it unfairly in the May 1917 Cooperative Study paper which he co-authored with his staff concerning tabulating the frequency curves. Fisher, believing that Pearson's criticism was unwarranted, responded with a paper which criticised examples in the Cooperative Study to the extent of ridiculing them. Fisher had looked again at his earlier correspondence with Pearson, noticed that many of his papers had been rejected, and concluded that Pearson had been responsible.
Sa pamamagitan ng Mayo 1916 pa rin sila ng kaukulang sa mabuting paraan. Subalit Pearson gusot ang assumptions ng Fisher 's pinakamataas na posibilidad na paraan, at criticised ito unfairly sa May 1917 kooperatiba Study papel na kung saan siya co-authored sa kanyang mga tauhan ng tungkol sa tabulating ang dalas kurva. Mangingisda, paniniwalang na ang Pearson's pamimintas ay hindi sapilitan, tumugon sa isang papel na criticised halimbawa sa mga kooperatiba ng Pag-aaral sa lawak ng ridiculing ang mga ito. Mangingisda ay tumingin muli sa kanyang mga naunang sulat sa Pearson, napansin na marami sa kanyang mga papeles ay tinanggihan, at concluded na Pearson had been responsable.