Bean bags
Cellophane that is going to be formed into bags for items such as dried beans or bird seed is passed over a light sensor to test if the alignment is correct before it passes through the heating units that seal the edges. Small adjustments can be made by the machine automati- cally. But if the alignment is too bad, the process is stopped and an operator has to manually adjust it. These misalign- ment stops occur randomly and independently. On one line, the average number of stops is 52 per 8-hour shift.
a) What is the mean number of stops per hour?
b) What is the standard deviation of stops per hour?