Question

The grades of a science test are normally distributed. Thanh finds that his grade on the test has a z-score of –2.5. Which statement must be true?

Answer 1

From all those aforementioned, the true statement is: Thanh’s grade is 2.5 standard deviations below the mean of the test grades. 

Answer 2

Explanation:

Given that the grades of a science test are normally distributed.

Also given that Thanh finds that his grade on the test has a z-score of –2.5

From this information we can find out the percentile of Thanh.

`P(Z<-2.5) = 0.5-04901 = 0.0099`

=1%

i.e. only 1% of the students were below Thanh grade and nearly 99% were above his grade

It is high time that Thann improves his scores as he is at 1st percentile only