The MLPowSim software is now available as version 1.0 Beta 1. We must stress here that MLPowSim is free software and comes with no WARRANTY whatsoever. Below you will find the software and manual along with two accompanying datasets. The manual has been written by William Browne, Mousa Golalizadeh and Richard Parker with the software written by William Browne and Mousa Golalizadeh.
MLPowSim was funded by the ESRC Grant: Sample size, Identifiability and MCMC Efficiency in complex random effect models. Further details can be found at Sample size and MLPowSim.
- There is a bug in the latest version of MLwiN 2.10 with regard the multivariate normal random number generator that means some MLPOWSIM code will cause MLwiN to crash upon attempted execution. The same code will however work fine in version 2.02. This will affect any files created by MLPOWSIM that contain the command MRAN. Fixed in version 2.11.
- The 1 level Binomial and Poisson models throw up an error message in MLwiN. This can be cured by replacing the file PRE in the discrete sub-directory of the MLwiN install with the following version
PRE. It has also been observed that on some systems were the user does not have administrator rights the macros run much slower in MLwiN 2.10 for binomial and Poisson models as compared to earlier versions of MLwiN. Fixed in version 2.11
- In R, the use of the PQL method for non-normal responses has been removed from the lmer function in later version of the function. Thus you may find that the PQL method can therefore not be used and so you will need to choose a different estimation procedure.
Other Multilevel Sample Size software
- The PinT software (Tom Snijders, Roel Bosker, and Henk Guldemond) used for comparison in the manual.
- The ML-DEs software package (Cools, Van den Noortgate and Onghena) that has been developed independently from MLPowSim but which also uses MLwiN and simulation to calculate power calculations for multilevel designs is available. We hope to compare MLPowSim with ML-DEs in further work.
- The OD (Optimal Design) software package (Steve Raudenbush and colleagues) also looks at multilevel power calculations and in particular cluster randomized designs.
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