SOLUTION: Assume that matric marks are standardised to have a mean of 52% and a standard deviation of 16% (and assume that they have a normal distribution). In a class of 100 students estima

Question 1133149: Assume that matric marks are standardised to have a mean of 52% and a standard deviation of 16% (and assume that they have a normal distribution). In a class of 100 students estimate how many of them:
a. pass (in other words get more than 33.3%);
b. get A's (more than 80%); and
c. get B's (between 70% and 80%).
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
z=(x-mean)/sd
>=(33.3-52)/16 or -18.7/16 or greater than -1.17
probability is 0.8790
or 88 students
more than 80% is >=(80-52)/16 or z>=1.75 or probability 0.0400 or 4 students
for 70%, >=(70-52)/16 or 1.125 or 0.1303. This is 13 students minus the 4 that get A or 9 students altogether.
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