{
  "id": 1316,
  "title": "questions answered multiple times by same user ?",
  "url": "/competitions/WhatDoYouKnow/discussion/1316",
  "author_name": "",
  "post_date": "2012-01-29T17:34:45.837Z",
  "votes": null,
  "comment_count": 3,
  "views": 2077,
  "content": "<p>It looks like there are entries indicating that the same user has answered the same question more than once, e.g. user_id = 85818 and question_id =&nbsp;3989, with different outcomes (the variable training is filled by the R benchmark script):</p>\r\n<pre><span style=\"font-family:andale mono,times\">training[training$user_id == 85818 &amp; training$question_id == 3989, ]</span><br><span style=\"font-family:andale mono,times\">&nbsp;&nbsp;&nbsp; correct outcome user_id question_id track_name subtrack_name</span><br><span style=\"font-family:andale mono,times\">32&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14</span><br><span style=\"font-family:andale mono,times\">218&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14</span></pre>\r\n<p>Is a question uniquely identified by the question_id or is the value of another column needed ?</p>",
  "messages": [
    {
      "id": "8333",
      "postDate": "01/29/2012 17:34:45",
      "content": "<p>It looks like there are entries indicating that the same user has answered the same question more than once, e.g. user_id = 85818 and question_id =&nbsp;3989, with different outcomes (the variable training is filled by the R benchmark script):</p>\r\n<pre><span style=\"font-family:andale mono,times\">training[training$user_id == 85818 &amp; training$question_id == 3989, ]</span><br><span style=\"font-family:andale mono,times\">&nbsp;&nbsp;&nbsp; correct outcome user_id question_id track_name subtrack_name</span><br><span style=\"font-family:andale mono,times\">32&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14</span><br><span style=\"font-family:andale mono,times\">218&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14</span></pre>\r\n<p>Is a question uniquely identified by the question_id or is the value of another column needed ?</p>",
      "rawMarkdown": "",
      "votes": null
    },
    {
      "id": "8336",
      "postDate": "01/29/2012 18:31:56",
      "content": "<p>Have you looked at the date stamps? If things are sorted as I think they are, it looks like he got it correct when he got back to it after 200 other questions...</p>",
      "rawMarkdown": "",
      "votes": null
    },
    {
      "id": "8339",
      "postDate": "01/29/2012 22:18:56",
      "content": "<p>good point ! Indeed, adding the 'answered_at' and 'date_of_test' columns, I get for this particular example:</p>\r\n<p><span style=\"font-family:andale mono,times\">&nbsp;&nbsp;&nbsp; correct outcome user_id question_id track_name subtrack_name&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; answered_at date_of_test</span><br>\r\n<span style=\"font-family:andale mono,times\">32&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14 2010-08-20 15:18:08&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;NA&gt;</span><br>\r\n<span style=\"font-family:andale mono,times\">218&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14 2010-08-22 14:08:14&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;NA&gt;</span><br>\r\n<br>\r\n(but I haven't systematically tested this for all duplicates found).<br>\r\n<br>\r\nSo I guess the simplest strategy would just be to take into account the newest answer (although even for the `answered_at` column, there seem to be NULL values).<br>\r\n<br>\r\nThanks !</p>",
      "rawMarkdown": "",
      "votes": null
    },
    {
      "id": "8341",
      "postDate": "01/30/2012 01:16:48",
      "content": "<p>And I might mention that a more fruitful strategy would be one that might allow for the user to get stronger as time goes on since he's actually studying...</p>",
      "rawMarkdown": "",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 8336,
      "author_name": "biasvariance",
      "author_url": "",
      "post_date": "01/29/2012 18:31:56",
      "content": "<p>Have you looked at the date stamps? If things are sorted as I think they are, it looks like he got it correct when he got back to it after 200 other questions...</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 8339,
      "author_name": "holzner",
      "author_url": "",
      "post_date": "01/29/2012 22:18:56",
      "content": "<p>good point ! Indeed, adding the 'answered_at' and 'date_of_test' columns, I get for this particular example:</p>\r\n<p><span style=\"font-family:andale mono,times\">&nbsp;&nbsp;&nbsp; correct outcome user_id question_id track_name subtrack_name&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; answered_at date_of_test</span><br>\r\n<span style=\"font-family:andale mono,times\">32&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14 2010-08-20 15:18:08&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;NA&gt;</span><br>\r\n<span style=\"font-family:andale mono,times\">218&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp; 85818&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3989&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 14 2010-08-22 14:08:14&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;NA&gt;</span><br>\r\n<br>\r\n(but I haven't systematically tested this for all duplicates found).<br>\r\n<br>\r\nSo I guess the simplest strategy would just be to take into account the newest answer (although even for the `answered_at` column, there seem to be NULL values).<br>\r\n<br>\r\nThanks !</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 8341,
      "author_name": "biasvariance",
      "author_url": "",
      "post_date": "01/30/2012 01:16:48",
      "content": "<p>And I might mention that a more fruitful strategy would be one that might allow for the user to get stronger as time goes on since he's actually studying...</p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "8333": "",
    "8336": "",
    "8339": "",
    "8341": ""
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  "source": "meta"
}