Spell-checking software catches “nonword errors,” which result in a string of letters that is not a word, as when “the” is typed as “teh.” When undergraduates are asked to write a 250-word essay (without spell checking), the number Y of nonword errors in a randomly selected essay has the following probability distribution.

a. Write the event “one nonword error” in terms of Y. Then find its probability.

b. What’s the probability that a randomly selected essay has at least two nonword errors?

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Value yi 2 3 4 Probability p; 0.1 ??? 0.3 0.3 0.1