Register Number: 3525

Total No. of Pages: 4

Name of the Candidate:

DIPLOMA EXAMINATION - 2011

(quality management)

(paper – Iii)

130. STATISTICAL PROCESS CONTROL

May) (Time: 3 Hours

Maximum: 100 Marks

Use of Statistical Table is permitted
Answer any FIVE Questions.
All questions carry equal marks.

UNIT – I

1. (a) State whether SQC is applicable only for a mass production industry? Justify your answer.
(10)

(b) Explain the procedure for constructing a control chart. (10)

(OR)

2. (a) When a process is said to be in a state of lack of control? Explain the reasons for it. (10)

(b) What is inspection? Discuss its objectives arid advantages. (10)

UNIT – II

3. (a) What is U-chart? Describe the essential steps involved in the control Chart. (10)

(b) The following are the inspection results of 100 metres of a piece of cloth.

Piece No / Number of
defectives
1 / 3
2 / 3
3 / 6
4 / 3
5 / 0
6 / 1
7 / 3
8 / 5
9 / 7
10 / 8

Determine the control limits for C-chart and state whether the process is under control.
(10)

(OR)

4. (a) Differentiate between (i) P-chart arid np-chart (ii) C-chart and U chart. (10)

(b) The number of students failing in a university exam was analyzed College wise. The
counts of failures notices in 15 colleges are as follows:

College Code / Number of
failures
A / 6
B / 12
C / 10
D / 10
E / 11
F / 13
G / 37
H / 31
I / 33
J / 38
K / 10
L / 11
M / 12
N / 10
O / 9

Analyze the data through an appropriate control chart and check whether the assignable causes at colleges are responsible for high failures. (10)

UNIT – III

5. (a) What are the criteria to be considered while deciding the frequency of sampling of
subgroups in mean charts. (5)

(b) The following data are the mean lengths and ranges of lengths of a finished product taken
from 20 samples each of size 5.

(OR)

6. (a) Write Shorts notes on: (i) Median Chart, (ii) Midrange Chart, and (iii) Moving
range chart (10)

(b) The following measurements are obtained from a sample of 5 items taken at regular
intervals from the manufacturing process.

(i) Determine the trial control limits.

(ii) Construct the X -R chart and plot the data.

(iii) What values of X and R you recommend for the future period.

(iv) If the specification limits are 1 ± 0.003 what do you conclude about the
process to meet the specifications. (10)

UNIT – IV

7. (a) Differentiate between Cp and Cpk indices. (5)

(b) A certain product has been statically controlled at a process average of 46.0 and a standard
deviation of 1.00. The product is supplied to two customers who have their own
specifications. The customer A sets a specification of 50.0 ± 4.0 and the customer B sets a
specification of 48.0 ± 4.0.

(i) Based on the conditions what percentage of the product produced will not meet the
specification requirements of customer A & Customer B.

(ii) Assuming that the two user’s needs were equal, a suggestion to shift the target to
49.0. At this suggested value what percentage of the product produced will not meet
the requirements of customer A & Customer B?

(iii) Do you think that this shift to a process target of 49.0 is desirable? (15)

(OR)

8. (a) What are the steps in the analysis of process capability? (10)

(b) What are the objectives of process capability Studies? Explain. (10)

UNIT – V

9. (a) Discuss the merits and demerits of special control charts. (10)

(b) Write short notes on:

(i) Co efficient of variation control Chart and

(i) Cumulative sum control Chart. (10)

(OR)

10. (a) Differentiate between Group control chart and Sloping control chart. (5)

(b) Plot a group control chart for the following record of measurements of the diameters of
part produced on each of the six spindles of an automatic screw cutting machine. The
values given are dimensions in units of 0.01 mm, in excess of 15 mm. (15)

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