The baking time of a ceramic plate is of interest. Too much time will cause the ceramic
plate to go black, and too little time will result in easy breaking. The specifications on
baking time are 10 +/- 0.2 min. Six plates are randomly selected, and their baking times
were noted. The sample means and standard deviations are calculated for 20 samples,
and the summarized results are presented below:
$$
\sum_{i=1}^{20} \bar{X_i} = 199.8
$$
$$
\sum_{i=1}^{20} s_i = 1.40
$$
a. What is the quality characteristic that we are monitoring? What type of control
charts (in general) would be used in this situation? Why?
b. Which specific type of control chart would be chosen for this case? Why?
c. What is the sample/subgroup size and number of subgroups/samples?
d. Set up a suitable control chart.
e. On the assumption that the baking time is normally distributed, what percentage of
the samples would you estimate to have baking time outside the specification limits
when the process is under control? (Note: Use the relationship o = sbar/c4)
(3+2+2+5+4=16M)