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3. A random variable X is given by its distribution table:

X -2 -1 1 2

P 0.1 0.3 0.2 0.4

Find its variance and standard deviation.

4. The distribution function of is given by

, if

, if 5

Find

5. Let be identically distributed independent random variables with standard deviation . What is the variance of their average ?

6. The digits of the numbers 202 and 101 are written on the cards and placed face down. Peter picks at random one of the cards of the number 202, and Paul picks at random one of the cards of the number 101. Find the mathematical expectation, variance and standard deviation of the sum of the digits on the two selected cards.

7.Discrete random variable X takes three values, -1, 0 or 1. Its mathematical expectation is equal to 0. Find the maximal possible value of its variance.

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