When it comes to the Titanic challenge, consider the naïve algorithm of just giving everyone a 39% probability of surviving, which is the overall proportion of survivors in the training set. This does not use any individual data, and is essentially the equivalent to predicting weather using climate records rather than information on the current circumstances. The Brier score for this ‘skill-less’ rule is 0.232. In contrast, the Brier score for the simple classification tree is 0.139, which is a 40% reduction from the naïve prediction, and so demonstrates considerable skill. Another way of
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