Hospital probability question

Question

The duration of routine operations in a certain hospital has approximately a normal distribution with an average of 145 minutes and a standard deviation of 13 minutes. What is the percentage of operations that last longer than 132 minutes? 

Answer 1

Given a normal distribution, with 145 minutes as the average, then +/-13 minutes gives a range of 132 to 158 minutes.

 

That range represents 68% of all operations, leaving 32% for the extremes. Of the extremes, half or 16% will be under 132 minutes, and half will be over 158 minutes.

 

So, the total percent which will take more than 132 minutes will be 84%.