Catching Up on Sleep It was found that Americans take on average 2.5 days per year to catch up on sleep. Assume the variable is approximately normally distributed and the standard deviation is 0.8 days. If a random sample of 25 individuals is selected, find the probability that the mean of the sample is less tha 2 days per year. Use The Standard Normal Distribution Table. Round the final answer to at least four decimal places and intermediate z value calculations to two decimal places. P(X < 2) = X