Assuming a normal distribution for the delivery time of sandwiches by Sammy's Sandwich Shop. We would apply the formula for normal distribution which is expressed as
z = (x - u)/s
Where
x = delivery times
u = mean delivery time
s = standard deviation
From the information given,
u = 25 minutes
s = 2 minutes
We want to determine the z-score for the number of sandwiches delivered in less than 23 minutes. It becomes
