Practice Problems
1. (Video 1) A fast-food restaurant has just installed a new ketchup dispenser. The amount of ketchup dispensed by the machine follows a normal distribution with mean 1.05 ounces and standard deviation of 0.08 ounce.
The restaurant’s goal is to get between 1.0 and 1.12 ounces of ketchup dispensed each time. What % of the time will that happen? (Answer: ~54%)
2. (Video 2) Suppose the manager adjusts the machine’s settings so the mean amount of ketchup dispensed is now 1.1 ounces. What must be the new standard deviation so 99% of the burgers have between 1 and 1.2 ounces of ketchup on them? (Answer: 0.039 oz)
Videos
Video 1: Determine Percents from Z scores
Note the video shows the wrong answer for the first practice problem. It should be about 54%).
Video 2: Percentiles to Scores (Z in reverse)
Cool Geogebra Applets to play with
https://www.geogebra.org/m/W9Nz53Ct
https://www.geogebra.org/m/p72a3qjZ