1
JEE Main 2018 (Offline)
+4
-1
If $$\sum\limits_{i = 1}^9 {\left( {{x_i} - 5} \right)} = 9$$ and

$$\sum\limits_{i = 1}^9 {{{\left( {{x_i} - 5} \right)}^2}} = 45$$, then the standard deviation of the 9 items
$${x_1},{x_2},.......,{x_9}$$ is
A
3
B
9
C
4
D
2
2
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
If the mean of the data : 7, 8, 9, 7, 8, 7, $$\lambda$$, 8 is 8, then the variance of this data is :
A
$${7 \over 8}$$
B
1
C
$${9 \over 8}$$
D
2
3
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
The mean of set of 30 observations is 75. If each observation is multiplied by a non-zero number $$\lambda$$ and then each of them is decreased by 25, their mean remains the same. Then $$\lambda$$ is equal to :
A
$${1 \over 3}$$
B
$${2 \over 3}$$
C
$${4 \over 3}$$
D
$${10 \over 3}$$
4
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
The sum of 100 observations and the sum of their squares are 400 and 2475, respectively. Later on, three observations, 3, 4 and 5, were found to be incorrect. If the incorrect observations are omitted, then the variance of the remaining observations is :
A
8.25
B
8.50
C
8.00
D
9.00
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