Hello community,
I have encountered in a serious trap multiple times. When doing OG2017 DS section (almost finished btw), I have made quite many mistakes when trying to choose between answer choices C and E. I succeed to identify that A and B are insufficient separately, but then I choose wrong answers, I don't know why.
Most of the time I chose E, but it turned out to be C. Choosing C, seldom turns out to be E, however. But it is almost equal throughput. 9 E to C and 6 C to E mistakes.
Our dear experts, does anyone have any advice how to tackle such a hurdle?
Thank you for your help in advance,
Artur
DS answer choice mistakes
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- ceilidh.erickson
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Without seeing your work, it's impossible to say for sure what your mistake is, but it's likely that you don't yet have a solid DS process.
Here is a very comprehensive list of resources for DS strategy and common DS mistakes: https://www.beatthegmat.com/data-suffici ... tml#797668
Start by reading this.
And here are some common mistakes based on the answers you described:
"Answer was C but I chose E"
It's likely that your notation is faulty. You correctly see that stmts 1 & 2 are insufficient on their own, but you don't write down what you *do* learn from them. When you combine the stmts, you're missing key pieces of what they give you. Here's a very simplistic example:
Q: what is the value of x?
(1) x^2 = 16
"Not sufficient because squares have multiple values"
(2) x < 0
"Not sufficient because infinite values"
(1) & (2)
"Both stmts give multiple values, so must not be enough. E."
Here, if the student had written:
(1) x = 4 or -4
(2) x neg
... it would be much easier to see that combining them narrowed it to one possible value. Try writing more down!
"Answer was E but I chose C"
This usually happens when students make assumptions: "they didn't work separately, but I bet they work together." Never assume sufficiency - always test values to try to prove *insufficiency*.
Here's a common example from OG 2016, DS #113:
(2) "Not sufficient because we don't know about r."
(1) & (2)
"We have info about all 3, looks like they're all 1. Sufficient."
Wrong! Try testing r = -1, s = -1, t = -1. Or r = 1/2, s = 2, t = 1/2. The product of all 3 might not be 1, so it's insufficient.
Hope this helps!
Here is a very comprehensive list of resources for DS strategy and common DS mistakes: https://www.beatthegmat.com/data-suffici ... tml#797668
Start by reading this.
And here are some common mistakes based on the answers you described:
"Answer was C but I chose E"
It's likely that your notation is faulty. You correctly see that stmts 1 & 2 are insufficient on their own, but you don't write down what you *do* learn from them. When you combine the stmts, you're missing key pieces of what they give you. Here's a very simplistic example:
Q: what is the value of x?
(1) x^2 = 16
"Not sufficient because squares have multiple values"
(2) x < 0
"Not sufficient because infinite values"
(1) & (2)
"Both stmts give multiple values, so must not be enough. E."
Here, if the student had written:
(1) x = 4 or -4
(2) x neg
... it would be much easier to see that combining them narrowed it to one possible value. Try writing more down!
"Answer was E but I chose C"
This usually happens when students make assumptions: "they didn't work separately, but I bet they work together." Never assume sufficiency - always test values to try to prove *insufficiency*.
Here's a common example from OG 2016, DS #113:
(1) "Not sufficient because we don't know about t."Is rst = 1?
(1) rs = 1
(2) st = 1
(2) "Not sufficient because we don't know about r."
(1) & (2)
"We have info about all 3, looks like they're all 1. Sufficient."
Wrong! Try testing r = -1, s = -1, t = -1. Or r = 1/2, s = 2, t = 1/2. The product of all 3 might not be 1, so it's insufficient.
Hope this helps!
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education