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Re: Fifteen college seniors, none of whom took any math classes [#permalink]
Q1: Among the points representing those students who study less than 25 hours, the highest is the second from the right whose score can be read on the y axis as 154 (C)

Q2: The three students with the highest GRE scores have studied roughly 28, 43 and 45 hours. Thus the mean is 28+43+45/3 = 38.6 which can be rounded to 39. (D)

Q3: To compute the ratio of those scoring less than expected, we can compute the denominator as the sum of the points after 20 hours of study and at the numerator those below the fit line. This leads to a ratio of 3/10
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Re: Fifteen college seniors, none of whom took any math classes [#permalink]
IlCreatore wrote:
Q1: Among the points representing those students who study less than 25 hours, the highest is the second from the right whose score can be read on the y axis as 154 (C)

Q2: The three students with the highest GRE scores have studied roughly 28, 43 and 45 hours. Thus the mean is 28+43+45/3 = 38.6 which can be rounded to 39. (D)

Q3: To compute the ratio of those scoring less than expected, we can compute the denominator as the sum of the points after 20 hours of study and at the numerator those below the fit line. This leads to a ratio of 3/10


Why did we have to consider the student who's marks came to what was expected, as his score was almost on the best fit line. Shouldn't the answer be \(\frac{2}{10}\) instead?
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Fifteen college seniors, none of whom took any math classes [#permalink]
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OE

1)

Quote:
We ignore all the points that are at 25 hours studied and more: that’s the point on the vertical 25-hour line and all the points to the right—all of those are ignored. The only ones we care about are the ones less than 25-hours. Of these, the highest is the one furthest to the right, at a height of 154. This person studied less than 25 hours and got a GRE Q score of 154.

Answer = (C)


2)
Quote:
The three highest scores, the three highest dots on the graph, are

a) person with Q = 165 who studied 45 hours
b) person with Q = 170 who studied 29 hours
c) person with Q = 169 who studied 44 hours
We don’t need a calculator. Subtract 30 from each hour amount for simplicity. Then we have hours of {15, –1, 14}. The sum of those is 28, and 28/3 = 9.33. Add back 30 now: that’s an average of 39.33. The closest answer choice is 39.

Answer = (D)



3)

Quote:
we have to look in the right part of the graph. We have to look at all the dots to the right of the 20-hour line: these are the only dots that count. Dots above the line are students who exceeded the prediction. Dots below the line are students who fell short of the prediction.


Attachment:
screenshot.89.jpg
screenshot.89.jpg [ 96.54 KiB | Viewed 3793 times ]


The gray dots on the left are out, because those are times less than 20 hours. Of the remaining dots, the 7 green dots are above the line and 3 red dots are below the line. Ten dots altogether are above the 20-hour line, and 3/10 performed worse than expected.

answer is 3/10
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