Statistics question: need help on how to figure this out?

Statistics question: need help on how to figure this out?


The professor has determined that the scores in his course are distributed with a mean of 75 and a standard deviation of 5. He announces that the top 10% of the scores will earn a "A". What is the lowest score a student can receive and still get A?

Statistics question: need help on how to figure this out?
assuming that the test scores are normally distributed then the scores that are above 1.28155 standard units about the mean.





Let X the the test score





P[ X %26gt; x ] = 0.1


P[ Z %26gt; 1.28155 ] = 0.1 where Z is the standard normal





(x - 75) / 5 = 1.28155





x = 81.40775





so anyone with a score of 81.40775 will get an A