Quality Analyst wants to construct a control chart for determining whether three machines (samples), all producing the same product, are under control with regard to a particular quality variable. Accordingly, he sampled four units of output from each machine, with the following results: [6 marks]

Machine

1. #1 17 15 15 17

2. #2 16 25 18 25

3. #3 23 24 23 22

1. What are the x-bar chart upper and lower control limits? [4 marks]

2. For upper and lower control limits of 23.29 and 16.71, which machine(s), if any, appear(s) to have an out-of-control process mean? [2 mark]

Measurements

15

3b) The Chair of the Operations Management Department at Quality University wants to construct a p-chart for determining whether the four instructors teaching the basic P/OM course are under control with regard to the number of students who fail the course. Accordingly, he sampled 100 final grades from last year for each instructor, with the following results: [9 marks]

Instructor Prof. A Prof. B Prof. C Prof. D

Number of Failures 13 0 11 16

1. What are the upper and lower control limits using appropriate control charts that would provide the 95.5 (probability).? [4 marks]

2. Using 95.5 (probability) which instructor(s), if any, should he conclude is (are) out of control? [2 mark]