the average mark on a set of university entrance exams was 70% with a standard dev. of 9.6. In order to be accepted into university, a student had to achieve a mark of 60% of better. If 800 students wrote the exam, approximately how many were accepted?
z-score = 800 - 60??/9.6
What am I doing wrong?
You are using your z formula wrongly.
What is the value of x, the percentage that you are looking for?
What is the value of mu, the mean/average percentage that was given?
Form that, you get the z score and the probability that any student gets above 60%.
That's for 1 student. What is the expectation with 800 students? (Hint: Expectation = np)
OK. z= 60-70/9.6 = -1.04 the probability is 0.1492
800 x 0.1492 = 119.36
"In mathematics, you don't understand things. You just get used to them." -- Johann von Neumann
Originally Posted by terminator
The probability that you got is the probability of a student of getting less than 60%, that is the probability that they were not accepted. To help you, always make a sketch of the normal distribtution and shade the area that you are required to find. You table gives values to the left of the z score while you are looking for the probability to the right of the z score.
thanks. really really helpful