Based on a sample of six cases, the mean incubation period for a gastrointestinal disease is 26.0 days with a standard deviation of 2.83 days. The population standard deviation () is unknown, but
= 28.0 days. Assume the data are normally distributed and normalize the sample mean. What is the probability that a sample mean would fall below 24 days based on this normalized statistic t where the actual standard deviation is unknown and the sample estimate must be used.