Bunuel wrote:
What is the probability that Lee will make exactly 5 errors on a certain typing test?
(1) The probability that Lee will make 5 or more errors on the test is 0.27.
Exactly 5 errors + More than 5 errors = 0.27
No information about fewer than 5 errors
Insufficient(2) The probability that Lee will make 5 or fewer errors on the test is 0.85.
Fewer than 5 errors + Exactly 5 errors = 0.85
No information about More than 5 errors
InsufficientCombining both :
(=> 5 errors) + (=< 5 errors)
= 0.27 + 0.85
= 1.12
Now, notice how a probability can not be more than 1, so the extra value obtained i.e 0.12 must be that of the exact 5 errors.
And since the probability of exact 5 errors is added
twice while combining both statements(
once from each statement), half of the extra value obtained must be the probability of
exactly 5 errors on a certain typing testTherefore, 1.12 - 1 = 0.12
Half of 0.12 = 0.06
SufficientHence,
C.