One more stats question.....?
Here is the question:
A school is administering a final examination. Assume that the length of time required to complete the test is normally distributed with a mean of 60 minutes and a standard deviation of 13 minutes. How much time must be allowed by the proctors if the school wishes to assure enough time for only 85% of the applicants to complete the exam?
Not quite sure where to start or what formula to use....
- Dr DLv 71 decade agoFavorite Answer
if 85% of the students finish the exam, then you could say the probability of finishing is 0.85.
Or the prob of finishing within the allotted timeframe is 0.85.
So find T such that P(X < T) = 0.85
The corresponding Z value would be
Z = (T - 60) / 14
From normal tables, this value is Z =~ 1.04
T = 74.6 mins.