Question

The average time taken to complete a test follows normal probability distribution with a mean of 70 minutes and a standard deviation of 25 minutes. The probability of a randomly selected student completing the test in 45 minutes or less is approximately equal to ____%. The probability of a randomly selected student completing the test in 95 minutes is ____%.

Answer 1

Under 45 mins is roughly 16%. This is because 68% of the curve exists within 1 SD of the mean. So 16% must be outside and smaller and 16% outside and larger (on average). 

It is impossible to determine how likely you are to find someone with exactly the second amount. However, if you are looking for that or less, you would get 84%