Typing errors in a text are either nonword errors as when th

Typing errors in a text are either nonword errors (as when \"the\" is typed as \"teh\") or word errors that result in a real but incorrect word. Spell-checking software will catch nonword errors but not word errors. Human proofreaders catch 70% of word errors. You ask a fellow student to proofread an essay in which you have deliberately made 10 word errors.

if x is the number of word errors missed, what is the distribution of x?

a. x is approx normal with

Solution

1. x is binomial with n = 10 and p = 0.3

2. y.is binomial with n = 10 and p = 0.3

n = 10

Proprtion of errors caught, p₁ = 0.70

Therefore, mean of errors caught = n.p₁ = 10 x 0.70 = 7

And, standard deviation = n.p₁.(1-p₁) = 10 x 0.70 x 0.30 = 2.1

Proprtion of errors missed, p₂ = 0.30

Therefore, mean of errors missed = n.p₂ = 10 x 0.30 = 3

And, standard deviation = n.p₂.(1-p₂) = 10 x 0.30 x 0.70 = 2.1