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Talk Me Down -- Venn Diagrams

(I like the idea of the "Talk Me Down" segment on Rachel Maddow's show, where she has guests come in and try to talk her down about various worrying subjects. Since this blog is basically my stress therapy, I am going to start borrowing that idea, and ask you, my readers to talk me down.)

My head exploded last night when I saw my daughter's study guide for social studies. She's got a test today.

For the sake of argument, let's say it's about natural resources in WallyWorld and Dizzyland. Here is what the workbook gave her for the Venn diagram for resources in the two areas of WallyWorld and Dizzyland:

it isn't called a Venn diagram in the book, but it certainly uses the form. This is not how Venn diagrams (aka. set diagrams) are supposed to work!!!

The overlap area is supposed to contain things present in both sets. But the non-overlap areas are supposed to contain things that are not shared.

So if I see "iron ore" under WallyWorld, I shouldn't also see it in the overlap area and in Dizzyland. In fact, a proper Venn diagram, as I understand it, should only have elements appearing once anywhere on the graph. The location tells you what sets that element is a member of.

This diagram is useless if I want to quickly know what is only in WallyWorld. My daughter is confused by this diagram. I was confused when I first tried to quiz her on it. I had to read the entire diagram and think about it before I could form a question. One mark of a very bad diagram is that you have to take in the whole diagram before coming to any sort of conclusions. Among other things, diagrams are supposed to help you understand information by breaking it down, not force you to consume it all in one bite.

The only thing I can think of is that this diagram makes it easy to ask the questions: "What does WallyWorld have?" and "What does Dizzyland have?" and "What do they both have?" because if you're only going to ask those questions, you can just read the answers off the sections. Try answering "What does WallyWorld have that Dizzyland doesn't?"

But I still object to my daughter being taught incorrect math diagramming by her social studies book!

Before I flip my lid, will somebody please talk me down?