Confused on Powerscore's Logical Reasoning Forum

[Samus12]

In Powerscore's Logical Reasoning Bible, page 324 has a Some Train Diagramming Mini-Drill. I am confused on #'s 3 and 8, which are essentially the same problem. It's my understanding that the "some train" can work in any direction. So from #3, if G⟶H(some)⟷I; Shouldn't that mean that ALL G's are H's, and since some H's are I's, therefore some G's should be I's? If every single G is an H, and some H's are I's, how can there not be a G that is an I? I would understand if some G's were H's, and some H's were I's, then the scope between G's and I's does not necessarily have to overlap. But given the example above, it seems to me that there should be an inference that some G's are I's, however, the manual clearly says that no inference can be made. What am I missing here? Any help appreciated.

[fra]

You cant say that some Gs are Is because not all Hs are Gs.
I think that it's easier to think about if you use an example.
Let's say that you are looking at a group of people composed of 15 girls, all with brown hair, and 15 boys, also all with brown hair.
All girls have brown hair.
Some people with brown hair are boys.
BUT it would be incorrect to say that some girls are boys - the some train doesn't work that way!

It might be easier to see this if you prove it to yourself with a venn diagram.

[ilikebaseball]

In Powerscore's Logical Reasoning Bible, page 324 has a Some Train Diagramming Mini-Drill. I am confused on #'s 3 and 8, which are essentially the same problem. It's my understanding that the "some train" can work in any direction. So from #3, if G⟶H(some)⟷I; Shouldn't that mean that ALL G's are H's, and since some H's are I's, therefore some G's should be I's? If every single G is an H, and some H's are I's, how can there not be a G that is an I? I would understand if some G's were H's, and some H's were I's, then the scope between G's and I's does not necessarily have to overlap. But given the example above, it seems to me that there should be an inference that some G's are I's, however, the manual clearly says that no inference can be made. What am I missing here? Any help appreciated.

This confused me as well. The book explains that because of the direction of the all arrow, the H's group could be so big that just because all g's are h's and some i's are h's, g's and i's do not necessarily have to overlap

[Samus12]

Ok that makes sense that the intermediate group can be so large that the other two don't overlap. Thanks a lot for everyone's help, that was driving me nuts.