Scores on an English test are normally distributed with a mean of 78% and a standard deviation of 4.5%. Find the value of the first quartile.

Answer 1

you want Z such that P(Z>z) = 0.75
That means that Z >= -.674

.674*4.5 = 3.033

So, you want a score of at least 78-3.033 = 74.967

The 1st quartile ends at a score of 75%

You can play around with Z table stuff at

http://davidmlane.com/hyperstat/z_table.html

Answer 2

Thank you so much!!!