You don't have to mention school breaks, but you do have to fill out the average hours-per-week blank. So you would take the total hours and divide them by the full number of weeks in the span. This will dilute the true hours per week somewhat, but that's OK.
If I volunteered for a total of 80 hours over a period of 1.5 years that gives me 1.1 hrs/week. If I subtract summer vacation it was 1.3 hours/week. Each time I went, it was 4 hours. Can I list the start-end date as 1.5 years, weekly hours as 4 and state in the description that I went for twenty 4-hour visits, for a total of 80 hours? It just looks silly to say I volunteered for 1 hour per week...
If the shadowing was a hodgepodge of docs, then I'd list the one with the greatest number of hours first, using that contact info, and list individual name, specialty, date span, total hours, contact info for each of the others in the narrative.
I shadowed 3 doctors once each. I have a contact for one of them, but the other two have left my hospital. Do I need to track them down and ask if I can reference them both?
Did you start with a hypothesis, design a study protocol, collect data, come to a conclusion which added to human knowledge, and create a potentially publishable article? That would be Research for AMCAS purposes. Otherwise, it would be fine to list it under Other as a Special Project, just as one might for a thesis project or engineering design team project.
What if you worked in a bio lab for a year, learning lab techniques (not helping a post-doc, but practicing on your own) and designed a project but did not actually carry it out? I quit after a year because I felt I was getting more out of my clinical and teaching jobs and couldn't devote myself to three part-time jobs at once during school... I describe all this in the description, but "Research/Lab" is still the right designation, right?
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Also, for what it's worth, required fields on AMCAS this year:
Experience Type
Experience Name
Start Date
End Date
Contact's First/Last Name and Title
Phone number OR email
Average hours per week does NOT have a red asterisk next to it...
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And some more questions!
Under honors/awards/recognitions, aside from stuff like Dean's List, could I list language proficiences in the form of certificates for courses completed? Not courses in university, but my job offers correspondence courses for certification in the language.
I participate in an organization that would probably be considered most similar to social chair in a dorm or fraternity - i.e. I organize social events for the area. Would this go under "Leadership"? Or volunteering (non-clinical obviously)? Or "other"?