Unintentional memory effects in CNTFETs due to e.g. traps and surfactant molecules lead to unpredictable device and circuit performance and needs to be avoided. Four chemical cleaning procedures for a successful removal of surfactant molecules from carbon nanotubes in field-effect transistors are evaluated statistically. (J. Tittmann-Otto et al. in Journal of Applied Physics, 10.1063/1.4944835)