Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability of the Z score. This is for one student.
With 3 students, the probability would be 3 times as likely. Either-or probabilities are found by adding the individual probabilities.
The marks obtained by a number of students in a certain subject are approximately normally distributed
with mean 65 and standard deviation 5. If 3 students are selected at random from this group, what is the probability that at least 1 of them would have scored above 75
2 answers
http://davidmlane.com/hyperstat/z_table.html
2 answers