65. U.S. companies lose $63.2 billion per year from workers with insomnia. Workers lose WEB file an average of 7.8 days of productivity per year due to lack of sleep (Wall Street Journal, January 23, 2013). The following data show the number of hours of sleep attained during a recent night for a sample of 20 workers. Sleep 6 5 10 56995 95 8 786 98 9 6 10 8 What is the mean number of hours of sleep for this sample? What is the variance? Standard deviation? a. b