An airline wants to monitor the performance of their baggage handling crew on the daily flight from Oklahoma City to Dallas that is always filled to its 140 passenger capacity

They track the number of passengers that lose bags each flight for a two-week period. The data are displayed in the following table. Determine control limits for the appropriate chart and indicate any points that are out of control.

Day # # Bags Lost
1 3
2 4
3 3
4 2
5 5
6 7
7 6
8 8
9 1
10 7
11 6
12 2
13 1
14 7
What will be an ideal response?

Answer: This is attribute data, so a p-chart is called for. The upper and lower control limits are 0.076 and 0 and all samples fall comfortably within this range.

= =
=
= (0.0316)

Sp =
=
= 0.0148
UCL = + 3Sp LCL = - 3Sp
UCL = 0.0316 + 3(0.0148) LCL = 0.0316 - 3(0.0148)
UCL = 0.076 LCL = -0.013 ∴LCL = 0

Day # # Bags Lost P (# Lost/140)
1 3 0.0214
2 4 0.0286
3 3 0.0214
4 2 0.0143
5 5 0.0357
6 7 0.0500
7 6 0.0429
8 8 0.0571
9 1 0.0071
10 7 0.0500
11 6 0.0429
12 2 0.0143
13 1 0.0071
14 7 0.0500