C? Not sure if this is correct
Q: Is SD (A) > SD (B)?
1) Difference between ages of any two is always > 1. To get the smallest possible SD for A, we can assume:
8 students have age = 14.5
8 students have age = 15.5 (which still makes mean = 15)
Smallest possible SD(A)^2 = [16* (deviation of each number from mean)^2]/16
= 12 * 0.5^2/16 = 0.5^2
=>Smallest possible SD(A) = 0.5
No information on ages of ClassB. INSUFF.
2) Difference between ages of any two is always < 0.5 (6 months). To get the largest possible SD we can assume:
6 students have age = 11.75
6 students have age = 12.25 (mean is still 12)
=> The largest possible SD(B) = 0.25
No information about classA. INSUFF.
Combining 1 & 2:
Since the smallest possible SD(A) is greater than the largest possible SD(B) it must be true that
Hence SD(A) > SD(B)
"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."
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