1
JEE Main 2023 (Online) 31st January Morning Shift
Numerical
+4
-1 If the variance of the frequency distribution

$$x_i$$ 2 3 4 5 6 7 8
Frequency $$f_i$$ 3 6 16 $$\alpha$$ 9 5 6

is 3, then $$\alpha$$ is equal to _____________.

2
JEE Main 2023 (Online) 30th January Morning Shift
Numerical
+4
-1 The mean and variance of 7 observations are 8 and 16 respectively. If one observation 14 is omitted and a and b are respectively mean and variance of remaining 6 observation, then $$\mathrm{a+3 b-5}$$ is equal to ___________.

3
JEE Main 2023 (Online) 29th January Evening Shift
Numerical
+4
-1 Let $$X=\{11,12,13,....,40,41\}$$ and $$Y=\{61,62,63,....,90,91\}$$ be the two sets of observations. If $$\overline x$$ and $$\overline y$$ are their respective means and $$\sigma^2$$ is the variance of all the observations in $$\mathrm{X\cup Y}$$, then $$\left| {\overline x + \overline y - {\sigma ^2}} \right|$$ is equal to ____________.

4
JEE Main 2022 (Online) 29th July Morning Shift
Numerical
+4
-1 Let the mean and the variance of 20 observations $$x_{1}, x_{2}, \ldots, x_{20}$$ be 15 and 9 , respectively. For $$\alpha \in \mathbf{R}$$, if the mean of $$\left(x_{1}+\alpha\right)^{2},\left(x_{2}+\alpha\right)^{2}, \ldots,\left(x_{20}+\alpha\right)^{2}$$ is 178 , then the square of the maximum value of $$\alpha$$ is equal to ________.

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