LG Workbook, Grouping Rule Diagramming Drill, P14-15 #2 + #6

[niki_lauda]

read over the explanations but don't see what i've written is different or incorrect

P14, #2: R and S cannot be selected together

My Answer:

_R/S_ __ __ __ __ I _R/S_
(in) I
I
I

Book Answer:

R DOUBLE NOT ARROW S

CONFUSION: i don't understand why the R/S option cannot be used. I guess looking back at the rule R nor S does not neccessarly have to be selected. if they don't have to be selected then the DOUBLE NOT ARROW would work. perhaps the R/S notation is wrong because I falsely assumed R or S had to be chosen.

P15, #6: Either G or H, but not both, must perform

My Answer: Again I used the G/H dual option, but did not show the DOUBLE NOT arrow

_G/H_ __ __ __ __ __ l _G/H_
(in) l
l
l

BOOK ANSWER: the book used the dual option, but also used the DOUBLE NOT ARROW

G DOUBLE NOT H

CONFUSION: because the question states that G or H MUST preform, usage of the DOUBLE NOT ARROW would indicate that if one preforms the other does not OR they both do not preform. if one of them MUST preform why would the DOUBLE NOT arrow be used in this case?

[Jon Denning]

Hey Niki,

Thanks for the questions!

2. The fact that neither R nor S has to be selected (both could be out) is one reason we don't show the split option. Save that split-option for when one must be used to fill a spot. Another reason is that we tend to use the double-not arrow in Grouping situations, and the diagram in the drill makes it clear that this is a Grouping game scenario. when a variable is not certain to be used and is in a grouping situation, we go with the double-not arrow.

6. For this one, the fact that one of the two MUST perform means that the split option is acceptable, but the fact that they cannot both perform (cannot be together) is the reason for the double-not arrow. So that's one in the group (split option), but not both in (double-not arrow).

Hope that helps!