U.S. companies lose $63.2 billion per year from workers with insomnia. Workers lose 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.

a. What is the mean number of hours of sleep for this sample?
b. What is the variance? Standarddeviation?

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6 5 10 5 6 99 5 95 8 78 6 98 9 6 10 8 6