Contaminant concentration data show a normal distribution wi

Contaminant concentration data show a normal distribution with mean of 100 mg/L and s = 10 mg/L. The probability of a measured concentration in the range of 80 mg/L and 120 mg/L is _____ (Reporting format: input 0.50 for 50%).

Solution

s = 10

80 < X < 120

80 - 100 < X - u < 120 - 100

-20/10< (X - u ) / s < 20/10

-2< Z < 2

P(-2< Z < 2 )= 0.9545 (from the standard normal table )