rsarashi wrote:Web sites W receives order for its products every day. What is the standard deviation of the numbers of orders that Web sites W received daily for the past 5 days?
1) The average (arithmetic mean) number of orders that Web site W received per day for the past 5 days is equal to the greatest of the numbers of orders that Web site W received daily for the past 5 days.
2) The range of the numbers of orders that Web site W received daily for the past 5 days is equal to 0.
In ascending order, let the 5 values = a, b, c, d, e.
Statement 1:
Let the average = 10, implying that the sum = (count)(average) = 5*10 = 50.
Thus:
a+b+c+d+e = 50.
Since the greatest value is equal to the average of 10, e=10.
The 5 orders are as follows:
a, b, c, d, e=10.
Since 10 is the greatest value, none of the other 4 values can be greater than 10.
Thus, the maximum possible case for the 5 values is as follows:
a=10, b=10, c=10, d=10, e=10.
In the list above, a+b+c+d+e = 50.
If any of the values in blue are decreased, the sum will be LESS THAN 50.
Thus:
To yield the required sum of 50, a=10, b=10, c=10, d=10, e=10.
The resulting list illustrates the following:
For the greatest of the 5 values to be equal to the average of the 5 values, all 5 values must be THE SAME.
Since all 5 values are the same -- implying that none of the 5 values deviates from the mean -- the standard deviation is 0.
SUFFICIENT.
Statement 2:
For the range to be 0, all 5 values must be the same.
Since all 5 values are the same -- implying that none of the 5 values deviates from the mean -- the standard deviation is 0.
SUFFICIENT.
The correct answer is
D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
