uniform distribution

Question

The rate at which liquid plastic is poured into an injection molding machine is uniformly distributed and takes between 78 and 96 seconds to pour the liquid into the tank compartment.  what is the standard deviation for the time it takes to fill the tank.

Answer 1

For a continuous uniform distribution between a and b the standard deviation is given by  

 

σ = (1/√12)*(b - a)  

 

Here b = 96 and a = 78 so  

 

σ = (96 - 78)/√12 = 18/(2√3) = 9/√3 = 3√3 ~ 5.196