1
JEE Main 2021 (Online) 20th July Evening Shift
+4
-1
If the mean and variance of six observations 7, 10, 11, 15, a, b are 10 and $${{20} \over 3}$$, respectively, then the value of | a $$-$$ b | is equal to :
A
9
B
11
C
7
D
1
2
JEE Main 2021 (Online) 20th July Morning Shift
+4
-1
The mean of 6 distinct observations is 6.5 and their variance is 10.25. If 4 out of 6 observations are 2, 4, 5 and 7, then the remaining two observations are :
A
10, 11
B
3, 18
C
8, 13
D
1, 20
3
JEE Main 2021 (Online) 18th March Evening Shift
+4
-1
Let in a series of 2n observations, half of them are equal to a and remaining half are equal to $$-$$a. Also by adding a constant b in each of these observations, the mean and standard deviation of new set become 5 and 20, respectively. Then the value of a2 + b2 is equal to :
A
425
B
250
C
925
D
650
4
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
Consider three observations a, b, and c such that b = a + c. If the standard deviation of a + 2, b + 2, c + 2 is d, then which of the following is true?
A
b2 = 3(a2 + c2) + 9d2
B
b2 = 3(a2 + c2) $$-$$ 9d2
C
b2 = 3(a2 + c2 + d2)
D
b2 = a2 + c2 + 3d2
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