A quality analyst wants to construct a control chart for determining whether three machines, all producing the same product, are in control with regard to a particular quality variable. Accordingly, he sampled four units of output from each machine, with the following results:

$\backslash$table$[[$Machine$,$Obs.,,,$],[$#$1,17,15,15,],[$#$2,16,25,18,17],[$#$3,23,24,23,25]]$

Use the factor table to answer the following questions.