{"action":"closed","issue":{"url":"https://api.github.com/repos/scipy/scipy.org/issues/172","repository_url":"https://api.github.com/repos/scipy/scipy.org","labels_url":"https://api.github.com/repos/scipy/scipy.org/issues/172/labels{/name}","comments_url":"https://api.github.com/repos/scipy/scipy.org/issues/172/comments","events_url":"https://api.github.com/repos/scipy/scipy.org/issues/172/events","html_url":"https://github.com/scipy/scipy.org/issues/172","id":166708042,"number":172,"title":"Wilcoxon signed rank test \"pratt\" zero method bug","user":{"login":"BLMeltdown","id":20567696,"avatar_url":"https://avatars.githubusercontent.com/u/20567696?v=3","gravatar_id":"","url":"https://api.github.com/users/BLMeltdown","html_url":"https://github.com/BLMeltdown","followers_url":"https://api.github.com/users/BLMeltdown/followers","following_url":"https://api.github.com/users/BLMeltdown/following{/other_user}","gists_url":"https://api.github.com/users/BLMeltdown/gists{/gist_id}","starred_url":"https://api.github.com/users/BLMeltdown/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/BLMeltdown/subscriptions","organizations_url":"https://api.github.com/users/BLMeltdown/orgs","repos_url":"https://api.github.com/users/BLMeltdown/repos","events_url":"https://api.github.com/users/BLMeltdown/events{/privacy}","received_events_url":"https://api.github.com/users/BLMeltdown/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":1,"created_at":"2016-07-20T23:49:20Z","updated_at":"2016-07-20T23:52:46Z","closed_at":"2016-07-20T23:52:46Z","body":"Hello\r\nAs presented here:\r\nhttp://stackoverflow.com/questions/38454893/error-in-scipy-wilcoxon-signed-rank-test-for-equal-series?noredirect=1#comment64315624_38454893\r\n(without no answer to disprove it as a mistake from me), \r\nI wish to report that maybe there is a problem with the results of scipy.wilcoxon signed rank test;\r\n\r\nimport scipy as sp\r\nx1=[29.39958, 29.21756, 29.350915, 29.34911, 29.212635]\r\nsp.wilcoxon(x1,x1,zero_method=\"wilcox\",correction=True)  \r\nreturns statistic=0.0, pvalue=nan\r\n\r\nBut with zero_method=\"pratt\", it returns statistic=0.0, pvalue=0.043114446783075355 instead.\r\nI think there is a mistake there. The statistics (for z-score, if I am not mistaken) are the same, but the results are different for the p-value, while they should not, actually.\r\nWhen both series are identical, there should be no good p-value, but this is confident with alpha=0.05.\r\n\r\nMaybe \"pratt\" zero_method is wrongly implemented. It is said to be more conservative, but instead it has also constantly given better /lower p-values on a large array of test values."}}
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