Typing errors in a text are either nonword errors (as when the is typed as teh)
ID: 3149547 • Letter: T
Question
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.
Missing 3 or more out of 10 errors seems a poor performance. What is the probability that a proofreader who catches 70% of word errors misses exactly 3 out of 10?
a. 0.2668
b. 0.3248
c.0.3333
d. 0.3000
Explanation / Answer
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.
Missing 3 or more out of 10 errors seems a poor performance. What is the probability that a proofreader who catches 70% of word errors misses exactly 3 out of 10?
a. 0.2668
b. 0.3248
c.0.3333
d. 0.3000
Binomial probability used.
p=0.7
n=10
misses exactly 3 out of 10 is same as catches exactly 7 words out of 10
P(X=x) = (nCx) px (1-p)n-x
P(X=7) = (10C7) 0.77(1-0.7)10-7
P(X = 7) = 0.2668
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