Alcohol withdrawal occurs when a person who uses alcohol excessively suddenly stops the alcohol use. Studies have shown that the onset of withdrawal is experienced a mean of 40 hours after the last drink, with a standard deviation of 18 hours. A sample of 38 people who use alcohol excessively is to be taken. What is the probability that the sample mean time between the last drink and the onset of withdrawal will be 38 hours or less?

Carry your intermediate computations to at least four decimal places. Round your answer to at least three decimal places.