Premium
Power and sample size requirements for two‐part models
Author(s) -
Lachenbruch Peter A.
Publication year - 2001
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.812
Subject(s) - sample size determination , zero (linguistics) , statistics , power (physics) , sample (material) , construct (python library) , centrality , mathematics , statistical power , computer science , econometrics , physics , philosophy , linguistics , thermodynamics , programming language , quantum mechanics
Two‐part models assume the data has a probability mass at zero and a continuous response for values greater than 0. We construct tests based on the proportion of zeros and the difference among the positive values of a response giving rise to a two degree of freedom χ 2 test. This note gives the non‐centrality parameter and finds the power for the test. The power is compared to the simulation results in a recent paper. We derive sample size calculations. We note that some modifications of this procedure may provide better tests if the non‐zero responses are discrete. Published in 2001 by John Wiley & Sons, Ltd.