Sunday, May 4, 2008

Lift Charts - TP, FP, KS, C - Key Words

  • The graph of a traditional lift chart in marketing is between Xaxis=Deciles and Yaxis=Cumulative Probability of True Identification of Consumers (True Positive - TP curve).
  • We can also create a lift curve for FP (false positives). This tells us the burden we have to bear (mistakes we commit) because we select the top decile, for example. The cumulative will give FP rate for any given cut of point selected, instead of top 10%.
  • In other words, we want to compare really TP and FP trade off and compare lift curves on the basis of area (or any other measure that provides one number which is independent of a cut off point)
  • This is done in KS statistics, where we measure maximum difference between TP and TN lift curves.
  • Alternatively we can do this (compare KS statistics or compare TP vs. FP curves) using C value from the SAS output.
  • Use c to judge comparative effectiness of lift curves

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