## Quick grouping game diagramming question

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flem

Posts: 12882
Joined: Mon Oct 10, 2011 6:44 pm

### Quick grouping game diagramming question

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?

Campagnolo

Posts: 906
Joined: Wed Oct 28, 2009 5:49 pm

### Re: Quick grouping game diagramming question

flem 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?

rinkrat19

Posts: 13923
Joined: Sat Sep 25, 2010 5:35 am

### Re: Quick grouping game diagramming question

Because you can have Y without having X, but you can't have X without Y.

timmydoeslsat

Posts: 148
Joined: Wed Aug 03, 2011 2:07 pm

### Re: Quick grouping game diagramming question

flem 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

flem

Posts: 12882
Joined: Mon Oct 10, 2011 6:44 pm

Thanks all