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Need clarification on formula

by msd_2008 » Sun Dec 07, 2008 6:23 pm
Can someone please explain to me how the following formulas differ in their applicability? Are both the formulas correct?

True # of objects = (total # in group 1) + (total # in group 2) + (total # in group 3) + (total # in none of the groups) - (# in only groups 1&2) - (# in only groups 1&3) - (# in only groups 2&3) - 2(# in all 3 groups)

AUBUC = A + B + C - AB - AC - BC + None - All.........note that we are not subtracting 2xAll in this formula.


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by dmateer25 » Sun Dec 07, 2008 6:50 pm
https://www.beatthegmat.com/very-interst ... t9806.html

Check this post. Stuart and Ron have a discussion on these formulas.
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by msd_2008 » Sun Dec 07, 2008 7:09 pm
I did go through the post. However, my query is still unresolved.
The post discussed a completely different question.....

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by dmateer25 » Sun Dec 07, 2008 7:17 pm
AUBUC = A + B + C - AB - AC - BC + None - All

Where did you come up with this?

It should be:

AUBUC = A + B + C - {A n B + B n C + C n A} + A n B n C



AUBUC = A + B + C - AB - AC - BC + None - 2(All): this formula is only applicable only when the groups are exlusive.
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by vivek.kapoor83 » Mon Dec 08, 2008 10:14 am
dmateer25 wrote:AUBUC = A + B + C - AB - AC - BC + None - All

Where did you come up with this?

It should be:

AUBUC = A + B + C - {A n B + B n C + C n A} + A n B n C



AUBUC = A + B + C - AB - AC - BC + None - 2(All): this formula is only applicable only when the groups are exlusive.
Dmatter,
pls elaborate wht dp u mean by exclusive groups ?

and
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by dmateer25 » Tue Dec 09, 2008 3:36 am
This is a quote from Ron.
before using the formula, just verify that 'group1&2', etc. are EXCLUSIVE; in other words, that they refer to the members of EXACTLY two groups. this is something that can't be implied; the evidence must be found explicitly in the problem statement. (in this problem, the evidence is '...exactly two classes')
This quote refers to this formula:

AUBUC = A + B + C - AB - AC - BC + None - 2(All)
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