I am trying to understand the following question.
The height of adult males is normally distributed with a mean of 172cm and standard deviation of 8cm. If 99% of adult males exceed a certain height, what is this height? The Answer given 153.4cm. Here is what i understood so far:
Since the question says 99% of them exceeded a certain height, i am definetly sure the height is at the left hand side of the bell curve. Everything right to the height is 99%, and everything to the left is 1%. I need to use the formula Z = x-mean / sigma
The z score at 99% is 2.3, so 2.3 = x-172 / 8
However, I am not able to arrive at the correct answer, but if i swap x and mean from the equation, i get the answer. Why?
You might have forgotten to take the negative value. $\frac{x-\mu}{\sigma}=-2.33$, so $x=153.36\approx153.4$.