Problem

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I am confused on how we established rules 5 and 6. I wrote it like like Z--->F. It said F cannot be selected unless z is also selected. So it sounded like Z need to be selected (sufficient) for F to be selected (Necessary). Just a little confused thanks.

@chrlierusso04, "Unless" generally introduces the necessary condition, whereas the other part of the conditional statement must be negated to become sufficient condition. Rules 5 and 6 are thus properly diagrammed as: F -> Z If F is selected, Z must be selected. If Z is not selected, F cannot be selected W -> H If W is selected, H must be selected. Let me know if you have any further questions.

Why are rules 2-3 written as F <--/--> H and so on? Can "cannot both" be equated to "not both" which could be written as F --> ~H OR H --> ~F, creating the potential for both variables to be out? While "cannot both" suggests that both variables cannot be included, it does not mean that both necessarily have to be included. In other words, you can have both F & H out.

I'm a little confused. can't both F and H not be out. I know they both can't be in but can't both be out?

Hi @jrb970 @Vitali-Carias, You are correct in that “F and H cannot both be selected” would be diagrammed as: F ? NOT H H ? NOT F Similarly, M and Z cannot both be selected should be as follows: M ? NOT Z Z ? NOT M Good catch!