A control method causes the processor to execute: excluding one or more pieces of first vibration data from a plurality of pieces of vibration data stored in the memory, wherein the plurality of pieces of vibration data are acquired within one period, wherein vibration times associated with the one or more pieces of first vibration data are included in an operation period in which the user performed the operation with respect to the information terminal device, and wherein the operation period is specified based on the time in the log information stored in the memory; and updating the threshold value using at least one piece of vibration data in the plurality of pieces of vibration data from which the one or more pieces of first vibration data are excluded.