Marks on a Chemistry test follow a normal distribution with

Marks on a Chemistry test follow a normal distribution with a mean of 72 and a standard deviation of 12. Approximately what percentages of the students have scores below 60?

Solution

P( x < 60)

P( z < [60-72] / 12 )

P( z < -1)

using tables of normal distribution

P( z < -1) = 0.1587