1
JEE Main 2022 (Online) 28th June Morning Shift
Numerical
+4
-1

The mean and standard deviation of 15 observations are found to be 8 and 3 respectively. On rechecking it was found that, in the observations, 20 was misread as 5. Then, the correct variance is equal to _____________.

2
JEE Main 2022 (Online) 25th June Evening Shift
Numerical
+4
-1

If the mean deviation about the mean of the numbers 1, 2, 3, .........., n, where n is odd, is $${{5(n + 1)} \over n}$$, then n is equal to ______________.

3
JEE Main 2021 (Online) 1st September Evening Shift
Numerical
+4
-1
Let X be a random variable with distribution.

x $$-$$2 $$-$$1 3 4 6
P(X = x) $${1 \over 5}$$ a $${1 \over 3}$$ $${1 \over 5}$$ b

If the mean of X is 2.3 and variance of X is $$\sigma$$2, then 100 $$\sigma$$2 is equal to :
4
JEE Main 2021 (Online) 27th August Evening Shift
Numerical
+4
-1
An online exam is attempted by 50 candidates out of which 20 are boys. The average marks obtained by boys is 12 with a variance 2. The variance of marks obtained by 30 girls is also 2. The average marks of all 50 candidates is 15. If $$\mu$$ is the average marks of girls and $$\sigma$$2 is the variance of marks of 50 candidates, then $$\mu$$ + $$\sigma$$2 is equal to ________________.
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