title: Weka prediction (percentage confidence) - what does it mean?
body: <p>I've been teaching myself Weka and have learned how to build models and get predictions out of them (predictions using the CLI).</p>
  
  <p>When I run prediction on a data set from a previously built model I get a column that is the "prediction" also known as prediction confidence for each instance predicted.</p>
  
  <p>I know what percent confidence means but shouldn't all my predictions be the accuracy of my Weka Model?</p>
  
  <p>aka if I have a J48 Decision tree classifier with accuracy of 90%, shouldn't every classified instance using this model be 90% prediction confidence?</p>
  
  <p>Any one know how this percentage confidence is calculated or how I should read the error prediction and model accuracy when telling others about my model? Thanks</p>