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Quick grouping game diagramming question

Posted: Mon May 14, 2012 6:10 pm
by flem
This is probably simple, but I need someone to explain this to me. I'm usually good with necessary/sufficient type stuff but this rule is weird. Maybe it's because I've been at work all day.

Roughly:

In order for X to be picked, Y must be picked.

Intuitively it seems that this would be diagrammed as:

Y ------> X

However, the correct representation of this rule is apparently:

X ------> Y

Can someone please break down why I am retarded?

Re: Quick grouping game diagramming question

Posted: Mon May 14, 2012 6:15 pm
by Campagnolo
tfleming09 wrote:This is probably simple, but I need someone to explain this to me. I'm usually good with necessary/sufficient type stuff but this rule is weird. Maybe it's because I've been at work all day.

Roughly:

In order for X to be picked, Y must be picked.

Intuitively it seems that this would be diagrammed as:

Y ------> X

However, the correct representation of this rule is apparently:

X ------> Y

Can someone please break down why I am retarded?
Y must be picked. That makes it necessary and therefore the condition on the right. Sometimes the contrapositive makes more sense: If Y is not picked, what about X?

Re: Quick grouping game diagramming question

Posted: Mon May 14, 2012 6:16 pm
by rinkrat19
Because you can have Y without having X, but you can't have X without Y.

Re: Quick grouping game diagramming question

Posted: Mon May 14, 2012 6:19 pm
by timmydoeslsat
tfleming09 wrote: In order for X to be picked, Y must be picked.
Just think about what you know to be true from that statement.

What happens if we have X?

We would have to have Y. Therefore, X ---> Y

Re: Quick grouping game diagramming question

Posted: Mon May 14, 2012 6:21 pm
by flem
Thanks all