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 Rachael Wilkenfeld
PowerScore Staff
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Hi Kra211,

I'd really start here by focusing on what you got right, not wrong. There's more right than wrong in your reasoning, and you want to expand on that good work you've already done. You are correct that HSE :arrow: see solution, implement solution. The trick is that it's a biconditional. You didn't write anything that was inaccurate. That's the main error with conditional reasoning that will come to bite you on the test. Inaccurate will be more dangerous than incomplete, every time. So think of your work here as incomplete, not inaccurate. You got part of the way to where you needed to be, just not all the way.

As for how to get all the way there on your own, this is an unusual stimulus. I noted the biconditional by the use of the term unique. The HSE's are unique in this way. That means, if someone sees a solution, and implements it every time, that person has to be an HSE. By saying that something is unique to a group of people, that means if you see the unique thing, it's required to apply to that group of people.

Let's look at some more familiar examples.

The Earth is unique the solar system for having just one moon.
Just one moon :arrow: Earth.

Tom Brady is unique among quarterbacks for having seven Superbowl rings.
7 rings :arrow: Brady

Another way to think about it is by thinking of the meaning of the word "unique." If you are unique, you are the only one. Only is one of our necessary indicators. Unique represents the same idea here as only.

Ultimately though, conditional diagramming comes down to practice, practice, practice. The more you do it, the easier it becomes. Practicing hard questions, like this one, builds your conditional reasoning skills.

Hope that helps!
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Hi, thanks for the explanation! Is there a list of words that signal bi-conditionality or hidden conditionality that I could memorize? I know "all that is necessary" and "the only thing required" can signal bi-conditionality, are there any other common ones? Many thanks!
 Adam Tyson
PowerScore Staff
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I don't know if we have such a list, cleocleozuo, and even if we do it is likely not comprehensive because the authors are clever enough to come up with new ways to make this test challenging, but I can give you a few, some of which you have seen before:

"If and only if"

"If but only if"

"If this, then that, and vice versa"

"If this, then that; otherwise not."

"Invariably the only ones"

Be on the lookout for any others that combine sufficient and necessary terms when referring to a single variable or group, and ask yourself if it's a two-way street. If my second cousins are invariably the only ones who dress up for our family reunion, then if someone dresses up for the reunion they must be my second cousin, and if my second cousin is at the reunion they must, invariably, be dressed up. If one, then the other: a biconditional!

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