Video tape production

Control the number of defective spots in video production. The video tapes are produced according to the length of 4000 m. continuously inspect the surface of 20 video tapes (each volume is 350 m long) in a certain process.

The data of unqualified defect spots are as follows:

7

1

2

5

0

6

2

0

4

4

6

3

3

1

6

3

1

3

5

6