the u.s. national center for health statis- tics compiles data on the length of stay by patients in short-term hos- pitals and publishes its findings in vital and health statistics. a ran- dom sample of 21 patients yielded the following data on length of stay, in days

4 4 12 18 9 6 12
3 6 15 73 55 1 1
10 13 5 7 1 23 9

a. obtain and interpret the quartiles.
b. Determine and interpret the interquartile range.