title: What does it mean to normalize based on mean and standard deviation of images in the imagenet training dataset?
body: <p>In implementation of densenet model as in <a href="https://arxiv.org/pdf/1711.05225.pdf" rel="nofollow noreferrer">CheXNet</a> paper, in section 3.1 it is mentioned that:</p>
  
  <p>Before inputting the images into the network, we downscale the images to 224x224 and <strong>normalize based on the mean and standard edviation of images in the ImageNet training set</strong>.</p>
  
  <ol>
  <li>Why would we want to normalize new set of images with mean and std of different dataset?</li>
  <li>How do we get the mean and std of ImageNet dataset? Is it provided somewhere?</li>
  </ol>