alimad wrote:
List S and List T each contain 5 positive integers, and for each list the average (arithmetic mean) of the integers in the list is 40. If the integers 30,40,50 are in both lists, is the standard deviation of the integers in list S greater than the standard deviation of the integers in list T?
(1) The integer 25 is in list S
(2) The integer 45 is in list T
Using stimulus we know
S={30,40,50,-,-,} two unknown ; Mean is 40
T={30,40,50,-,-} two unknown ; Mean is 40
Lets use the quick "EYEBALL SD FROM MEAN" method .
Now the set which will have values far from 40 will have a greater SD
Stament(1) The integer 25 is in list S
It means our set is now complete S={25,30,40,50,55}
But it tells us nothing about element of other set.
INSUFFICIENT
(2) The integer 45 is in list T
Meaning now out set T is complete t={30,35,40,45,50}
But it tells that nothing about element of set S
INSUFFICIENT
MERGING BOTH
S={25,30,40,50,55}
T={30,35,40,45,50}
Lets use the quick "EYEBALL SD FROM MEAN" method .
SD of S will be greater since it extreme values are more spread out from the mean (40-25 =15 and 40-55=-15) Exact SD will be 12.7
SD of T will be lower since it extreme values are less spread out from the mean (40-30 =10 and 40-50=-10) Exact SD will be 7.9
ANSWER IS C
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