=+16. Hourly samples of size 3 are taken from a process that produces molded plastic containers, and a critical dimension is measured. Data from the most recent 20 samples is given here:

Hour x1 x2 x3 Hour x1 x2 x3 1 .36 .39 .36 11 .36 .32 .36 2 .33 .35 .30 12 .38 .47 .35 3 .51 .41 .42 13 .29 .45 .39 4 .42 .37 .34 14 .44 .38 .43 5 .39 .38 .38 15 .38 .37 .37 6 .33 .41 .45 16 .31 .43 .38 7 .43 .39 .41 17 .39 .49 .35 8 .41 .32 .32 18 .43 .36 .38 9 .37 .42 .36 19 .40 .45 .32 10 .26 .42 .32 20 .40 .40 .32