Spelling mistakes in a text are either "nonword errors" or "word errors." A nonword error produces a string of letters that is not a word, such as "the" typed as "teh." Word errors produce the wrong word, such as "loose" typed as "lose." Nonword errors make up 25% of all errors. A human proofreader will catch 80% of nonword errors and 50% of word errors. What percent of errors will the proofreader catch?
A)20%
B)37.5%
C)57.5%
D)80%

Question

Quizplus · Accepted Answer

Let's assume there are 100 errors.
Given that 25% of errors are nonword errors, which means 25 errors are nonword errors and 75 errors are word errors.
A human proofreader will catch 80% of nonword errors, which means the proofreader will catch 20 out of 25 nonword errors.
Also, the proofreader will catch 50% of word errors, which means the proofreader will catch 37.5 out of 75 word errors.
Therefore, the total number of errors caught by the proofreader will be 57.5 out of 100 errors, which is 57.5%.

Spelling Mistakes in a Text Are Either "Nonword Errors" or "Word