Students are asked to type two hundred and fifty words essey without using spell checking. The number of misspelled words, which is represented as the random variable X, has the following probability distribution:
Value of X: 0 1 2 3 4
Probability: 0.1 0.2 0.3 0.3 0.1
a. write the event "at least 2 misspelled words" in terms of random variable X. What is the probability of this event?
b. Calculate the expected value and the variance of X