The data collection protocol is the procedure for executing the above steps of the Plan to collect and record the data. It deals with management and adminstrative issues such as who does what and when. It also includes a plan for monitoring the data as they are collected to ensure quality.
Michelson gives us no indication of how he planned to record and monitor his data. However, the meticulous care he showed elsewhere in the planning of his study suggests that he would have been especially careful to ensure that the data were recorded as measured.
In today's context, amongst other issues, this step will include consideration of data entry, file structures, analysis software, and so on, especially for Plans in which a large amount of data is to be accumulated.