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Which technique prevents a zero count from destroying an estimate?

  • A.Replacing the zero with the average of the neighbouring counts
  • B.Adding a small constant to every count
  • C.Discarding the features whose counts have fallen to zero entirely
  • D.Rescaling all of the counts so that the smallest becomes one

Answer: B

Laplace smoothing adds a pseudocount to every cell before normalising, which keeps every probability strictly positive at a small cost in accuracy where data are plentiful. It amounts to a Dirichlet prior over the table. Discarding features loses information, rescaling distorts the ratios and neighbour averaging assumes an ordering that categorical values do not have. The Bayesian reading is what tells you how large the pseudocount should be.

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