This paper presents a comprehensive review and a specific example implementation of a minimally invasive technique that can be used to make quantitative measurements of a subject's Electro-Dermal Activity (EDA) in educational technology studies. The Q sensor is a low-cost wireless sensor that can be worn on the wrist to measure a subject's response to various stimuli in both laboratory and natural education research settings. The example application shown here is from a study on presence while viewing two different screen sizes used in a Virtual Reality (VR) system. It is recommended that EDA data be used in conjunction with other data, such as from other types of sensors and from qualitative instruments such as surveys, because human EDA response to a given environment and stimuli is not always consistent. EDA sensors show great promise as an effective tool that can be used in educational technology research.