Simply Statistics A statistics blog by Rafa Irizarry, Roger Peng, and Jeff Leek

Fundamentals of Engineering Review Question Oops

The Fundamentals of Engineering Exam is the first licensing exam for engineers. You have to pass it on your way to becoming a professional engineer (PE). I was recently shown a problem from a review manual: 

When it is operating properly, a chemical plant has a daily production rate that is normally distributed with a mean of 880 tons/day and a standard deviation of 21 tons/day. During an analysis period, the output is measured with random sampling on 50 consecutive days, and the mean output is found to be 871 tons/day. With a 95 percent confidence level, determine if the plant is operating properly. 

  1. There is at least a 5 percent probability that the plant is operating properly. 
  2. There is at least a 95 percent probability that the plant is operating properly. 
  3. There is at least a 5 percent probability that the plant is not operating properly. 
  4. There is at least a 95 percent probability that the plant is not operating properly. 

Whoops…seems to be a problem there. I’m glad that engineers are expected to know some statistics; hopefully the engineering students taking the exam can spot the problem…but then how do they answer?