Question

The Kirkland Company produces plastic bottles to customer order. The quality inspector randomly selects four bottles from the bottle machine every time (considered as one sample) and measures the outside diameter of the bottle neck, a critical quality dimension that determines whether the bottle cap will fit properly. The dimensions (in.) from the last six samples (each sample contains 4 bottles) are

Sample	Bottle #1	Bottle #2	Bottle #3	Bottle #4
1	0.624	0.627	0.584	0.600
2	0.597	0.601	0.607	0.613
3	0.582	0.570	0.589	0.592
4	0.620	0.605	0.595	0.585
5	0.582	0.617	0.698	.633
6	0.585	0.593	0.637	0.579

1. Assume that only these samples are sufficient, and use the data to determine control limits for the process. What SPC charts are needed here? What are the control limits?

2. Can you tell if the process is in statistical control?

Answer 1

We can use X-bar chart to understand the process quality