Question

Spell‑checking software catches nonword errors that result in a string of letters that is not a word, as when "the" is typed as "teh." When undergraduates are asked to type a 250‑word essay, without spell‑checking, the number X

of nonword errors has the provided distribution.

Value of X

	0

1

2

3

4

Probability	0.1

0.2

0.3

0.3

0.1

(a) Is the random variable X

discrete or continuous? Why?

Continuous, because there can be all sort of errors.

Discrete, because it has a finite number of possible values: 0,1,2,3,4

.

Discrete, because we do not know the number of errors in advance.

Continuous, because all the probabilities are between 0

and 1

.

(b) Which statements are equivalent to the event "at least one nonword error" in terms of X

? Select all that apply.

X≥1

X>0

X<1

X≥0

X≠0

What is the probability of the "at least one nonword error" event? Enter your answer within one decimal place.

P(nonword error)

=

Which one of the statements describes the event X≤2

?

more than 2

nonword errors

less than 2

nonword errors

no more than 2

nonword errors

at least 2

nonword errors

(c) What is the probability of the event X≤2

? Enter your answer within one decimal place.

P(X≤2)=

What is the probability of the event X<2

? Enter your answer within one decimal place.

P(X<2)=

Answer 1