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GMAT Prep: What is the median

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GMAT Prep: What is the median

by elaine1920 » Thu Jul 30, 2009 1:25 pm
A student worked for 20 days. For each of the amount shown in the first row of the table,the second row gives the numbers of days that the student earned that amount. What is the median amount of money that the student earned per day for the 20 days?

Amount earned per day: $96 , $84 , $80 , $70, $48
Number of days: 4 , 7, 4, 3, 2

A: $96
B: $84
C: $80
D: $70
E: $48

The answer is B

Guys, how to solve this question? thanks!
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by shahdevine » Thu Jul 30, 2009 3:26 pm
This is classic statistical analysis which involves histograms, and whether data skews left, right etc, based on whether the data clusters either at head or tail of data's shape.

Trick here is to look at days student earned that amount. The days represent the frequency of an observation. usually the amount earned which has the most days or frequency is where the median lies. In this case 84$ has 7 days where that amount was earned. The median is just the middle term...so the probability of the middle term being on the amount earned which had the most days would be highest.

cheers,

sd
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by tohellandback » Thu Jul 30, 2009 9:09 pm
there are 20 students in total. so the money spent by the 10th and the 11th student will give you the median.
the amount spent are
$96 , $84 , $80 , $70, $48 arranged in descending order.
Now if you count, both the 10 and 11th student in increasing or decreasing order have spent 84$
so median is 84+84/2=84
The powers of two are bloody impolite!!
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