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Event Iterations
How to Cycle (Repeat) Events
Event Iterations is one of nine types of Support Event (Guidance Events, Branching Point Event, Calendarize Event, Event Iterations, Event Array, Study Context Events, Unspecified Support Events, Randomized Event, and Goodbye Event.
The normal sequencing of events in the Execution List assumes that each event will be presented once. However, in many designs, the same treatments and events are executed more than once and often many times, as in human or materials performance testing. Imaging a car door slamming 10000 times and taking a materials fatigue test after each slam. We would have an impossibly long list of events in the Execution List. Other examples include Clinical Trials, where for two years an experimental drug is taken every two days followed by a blood pressure test.
ProtoGenie gives users the ability to cycle any event in the Execution List the desired number of times. This is much like using a "For/Nest" or "Do Loop" with an incrementer in basic programming to repeat an operation a given number of times. For the simple situation of the slamming car door or the experimental drug, simply click on the button labeled "Cycle Events" located between the Assembly and Event Names areas. In the box labeled "Number of cycles), set the number to the desired number of repetitions and that is all that is there is to it. In both of these cases, there are still only two events in the Assembly widow (plus support events).
Other situations require more options. For example, consider a typical times series study in which there is a sequence of the same measurement, a treatment, and another sequence of the same measurement. This situation is different from the clinical trial situation because the two events in the Execution List are cycled individually and the measurement event cycle is presented twice.
To set this sequence of events, select the event that is cycled first (which in this case, was the measurement) and click on "Cycle Events." Set the number of cycles to the desired number (e.g. 10). Return to the Execution List and click on the next event to be cycled and repeat the procedure above. Then, repeat all of the above for the measurement again. Now, when this protocol is executed, 10 measurements will be presented. Then, the treatment will be presented followed by another 10 measurements.
Other common situations in human performance testing get more complicated. In those studies, we are usually talking about what is called "Cross over designs" which means that the same person gets the same treatment more than once. One complexity is that measurement cannot be identical because subjects will tend to memorize and recognize the measurement when it comes up. This requires the presentation of the same basic measurement but on different but "equivalent materials." An additional complexity is that experimenters may want to cycle groupings of treatments and measurements rather than individual events. Both of these situations are treated on the next page under Sequencing In Repeated-Event Laboratory Testing.