Question

Part 3 [35 Marks 3- The number of nonconforming switches in samples of size 75 are shown in Table 3. [20 Marks] Table 3 Number of Nonconforming Assemblies Number of Sample Nonconforming Number Sample Number Assemblies 6 7 11 1 15 12 2 0 13 1 3 9 14 3 4 5 15 6 5 1 16 8 4 17 10 7 5 18 5 7 19 2 9 12 20 7 10 (a) Construct a fraction nonconforming control chart for these data. Does the process appear to be in control? If not, find out-of-control points and assume that assignable causes can be found [15 Marks] for all points outsi de the control limits and calculate the revised control limits. (b) What is the smallest sample size that could be used for this process and still give a positive lower control limit on the chart? [S Marks]

Answer 1

have a tixed Samplu Size n e Sample Tfrachion Bample fracton 75 far each number If di amd P ane Tspectve the numben onforg iomeonfer assemblies nono and th di (= (,2,. ,20 TABLE '. Con trol chant for fractn Computations for noncon- Sample Numper Sampl No 1 0.093 3 1 1 0 680 0 2 (2 0 2000 ( 3 0 0133 3 0 000 d12.00 0 08 00 0.0667 0 10 67 0-o133 0 1333 0-0533 00667 2 0-09 33 00933 lo 20 2 999.9 08533 0 7066 Totnd 2s Now have, 0-70(6 0-85 33 0.0780 20 2o -1-p = 1- 0- 07 80 0.922o 3-6 Contro Liwits fur p- chant Griven by Oune 0.0780 0.003S9 58 = 0.0 78o t0.179 3 UCL,0-2579 CLp P 0-0780 0.1019 ~o LCLP (Ngotive) Comtrol . So, te process appLan to be in vth smullerp sarpli size be uxd tun this procm and sill e a posihve lowen Sample numben that and 6 Coula Contnol iwnt chant

U.C L 1- C.L 2 16 26 2. Number Sample No. ractidM nomcon tor m'iny us emlolis