1
JEE Main 2021 (Online) 27th July Morning Shift
+4
-1
If the mean and variance of the following data : 6, 10, 7, 13, a, 12, b, 12 are 9 and $${{37} \over 4}$$

respectively, then (a $$-$$ b)2 is equal to :
A
24
B
12
C
32
D
16
2
JEE Main 2021 (Online) 25th July Evening Shift
+4
-1
The first of the two samples in a group has 100 items with mean 15 and standard deviation 3. If the whole group has 250 items with mean 15.6 and standard deviation $$\sqrt {13.44}$$, then the standard deviation of the second sample is :
A
8
B
6
C
4
D
5
3
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
4
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
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