Q7 - Those who participate in local politics

[nandy_millette]

I got this correct but during review I realized that I diagrammed one of the statements incorrectly;

SO here is my old diagram
1) All PLP-->PS and SO
2) All PLP-->CV (contrapositive ~CV-->~PLP)

Where
PLP= persons who participate in local politics
PS= genuinely interested in public service
SO= self opportunist
CV= influence community values

Upon review, I realised that my first statement was not correct. The stimulus says that PLP includes those who are PS and those who are SO. I realized that this was a hidden "some" statement and diagrammed it like so:

Some PLP are PS
Some PLP are SO

When we combine these statements with All PLP-->CV, we can make the following inferences:

1) Some PS are CV
2) Some SO are CV

A- Some SO are CV (correct answer)
B-some PS are ~CV- this maybe true but we cannot directly infer this from the statements given in the stimulus
C- All CV-->PLP: mistaken reversal- stimulus says All PLP-->CV
D- All that we know about CV is that 1) Some CV are PS and 2) some CV are SO, and 3) ~CV-->~PLP
E-All CV-->PS or SO, again like D above, we can only make three inference about CV and this is not one of them.

Did I accurately diagram the statement: PLP includes PS and SO?

[christine.defenbaugh]

nandy_millette, I want to commend you for catching your own mistake so handily!

Yes, your fix for the first statement is absolutely correct. Because all we know is that PLP includes PS and SO, we can't conclude that it is exclusively composed of those two groups! There may well be PLP who are neither!

And since "some" statements are reversible, some PLP are SO can be written some SO are PLP. And since we know that all PLP are CV, we can infer that some SO are CV!

I like to think of "some" statements in terms of "at least one". So, If local politics participation includes some selfish opportunists, then I know there's at least one guy, let's call him Bob, who is a selfish opportunist involved in local politics. And this guy, Bob, must have an influence on the community's values, since everyone involved in local politics does. So I know there's at least one guy, Bob, who is a selfish opportunist who also has an influence on the community's values!

Excellent work catching your own mistake, and nice eliminations!