Question

suppose a geyser has a mean time between 66 minutes. If the interval of the time between the eruptions is normally distributed with standard deviation 16 minutes. what is the probability that a randomly selected time interval between eruptions is longer than 74 minutes?

Answer 1

µ =    66                  
σ =    16                  
                      
P ( X > 74.00   ) = P( (X-µ)/σ ≥ (74-66) / 16)              
= P(Z > 0.500   ) = P( Z ≤ -0.500   ) =    0.3085   (answer)