Choice of the sampling device

A device that meets all the needs of researchers does not exist. The researcher who plans to buy or hire signaling devices faces a difficult decision. The starting point of the decision-making process should be a commonsense analysis of the purpose of the study and the nature of the target population. A pilot run with different devices before making hardware investments is recommended.

General choice considerations

The shape, size and use of the ESM device should create minimal disturbance for the subject and his environment. It should have flexible applicability and allow full control over the sampling process by the researcher.

Non-reactivity: The goal of many ESM studies is to gather an ecologically valid dataset. The ideal device should lend itself to the feeling that nothing strange is happening in daily life, for both subjects and their environment. Reactivity can best be minimized by using small, reliable and inexpensive devices that emit unpredictable signals and can be fully employed within a range of environmental constraints.

Size: Small devices usually create less reactivity. Large devices may be forgotten because they are not easily carried by the subject and require extra attention. This further increases the chances of unwanted reactions from the environment. A large device is no real problem if the sampling environment is relatively small or when the technological intrusiveness of the device is exploited to enhance compliance or reporting accuracy (Nelson, 1977).