Following is the record of the defectives observed during the inspection process of an automatic machine producing small bolts of standard size.

Sample Number Sample Size Number of Defective Bolts 1 25 3 2 50 5 3 45 1 4 55 2 5 35 –

Sample Number Sample Size Number of Defective Bolts 6 40 1 7 50 9 8 65 2 9 30 3 10 25 2 11 55 5 12 40 4 13 50 3 14 25 2 15 40 2

(a) Find p , UCL and LCL.

(b) Are the UCL and LCL constant?

(c) If not, what is the reason?

(d) Express the deviation from p (i.e. p – p ) in units of so many standard deviations.
Draw the control chart.