Furthermore, more conscientious students are more likely to grin and bear it, thus giving the A students a lower rate of reporting.

I agree, but that still doesn't explain why the reported death rate for grandmothers is 24 times higher than that for grandfathers.

I suppose it's possible students care about their grandmothers more than their grandfathers.

Men also die earlier than women so it's possible most students grandfathers are already dead before they reach college. I know this was the case for me.

There's not really an age when women outnumber men 24:1 though [1]

[1] Figure 2, http://cnx.org/content/m42935/latest/?collection=col11407/la...

For me as well. And I have three grandmothers, courtesy of my stepmother. Two of them died while I was in college, the third is 97 y.o., and I've got two more semesters to go, so there's a chance I may be one of those people who dips into the "negative grandmothers" category.

This is a very good point. Both my grandfathers passed away when I was young (i.e. before I took any important exams), whereas both my grandmothers are still alive and kicking.

Along the same lines: for a young college student the death of a grandparent might very well constitute the first experience of losing a family member. With little experience, it's not always clear how these situations should be handled with respect to work or school. More mature individuals are more likely to handle deaths within the family with discretion.

With increasing age it is also more likely that you've already had your grandparents die.