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Table 2 Louse-free Rate the Day After Final Treatment (PP population)

From: A randomised, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children - melaleuca oil and lavender oil, pyrethrins and piperonyl butoxide, and a "suffocation" product

     P-value
   Number Louse-free Louse-free Percentage Unadjusted Adjusted*
Louse-free rate:
Tea Tree/Lavender Oil product versus
Pyrethrins/piperonyl butoxide product
Tea Tree/Lavender Oil product 40 out of 41 97.56 < 0.0001 *
  Pyrethrins/piperonyl butoxide product 10 out of 30 33.33   
Louse-free rate:
Suffocation product
versus
Pyrethrins/piperonyl butoxide product
Suffocation product 37 out of 37 100 < 0.0001 *
  Pyrethrins/piperonyl butoxide product 10 out of 30 33.33   
  1. *The adjusted p-values could not be calculated because the generalized Hessian matrix was not positive definitive (the off-diagonal elements are too few)