Solution: f(x)= 1/3, x∈

p(X & gt； 3)=∫ (the upper limit is 5 and the lower limit is 3) 1/3dx.

=2/3

Three independent observations satisfy the binomial distribution b ~ (3,2/3)

At least twice, p = 3 * (1/3) * (2/3) 2+(2/3) 3 = 20/27.

Extended data:

Random variables may take different values under different conditions due to accidental factors, so they are uncertain and random, but the probability that these values fall within a certain range is certain. Such variables are called random variables. Random variables can be discrete or continuous.

For example, the measured value in the analysis test is a random variable with probability, and the measured value may change randomly within a certain range. The specific value can not be determined before measurement, but the measurement result is certain, and the measured value obtained by repeated measurement has statistical regularity.

The essential difference between the uncertainty of random variables and the uncertainty of fuzzy variables is that the measurement results of the latter are still uncertain, that is, fuzzy.

Baidu Encyclopedia-Random Variable