Code: A-32 Subject: RELIABILITY AND QUALITY CONTROL
Time: 3 Hours
Max. Marks: 100
NOTE: There are 11 Questions in all.
Question 1 is compulsory and carries 16 marks.
Answer to Q. 1. must be written in the space provided for it in the answer book
supplied and nowhere else.
Answer any THREE Questions each from Part I and Part
II. Each of these questions carries 14 marks.
Any required data not explicitly given, may be
suitably assumed and stated.
Q1. Choose the correct or best alternative in the following: (2x8)
a. A
system consists of two units in series with hazard rates 
. The hazard rate of the system is:
(A) 
. (B)
.
(C) 
. (D)
.
b. If the ratio of MTTR to MTBF is r, the inherent availability of the equipment is equal to:
(A) 
(B)
(C) 
(D)
c. Which of the following statement is not correct for the electronic components
(A) Reliability
data is well documented.
(B) Life testing is possible.
(C) Mode of failure is complex.
(D) Constant hazard rate normally applies for longer duration.
d. The reliability of a system consisting of two parts with respective reliabilities of 0.7 and 0.8 and connected in parallel, is
(A) 0.44 (B) 0.56
(C) 0.66 (D) 0.94
e. The upper trial control limits of the control chart for fraction defective is:
(A) 
(B)
.
(C) 
(D)
f. If the standard deviations of two mating parts are 0.03 mm and 0.04 mm respectively, then the standard deviation of the clearance of the mating parts will be
(A) 0.01 mm (B) 0.265 mm
(C) 0.05 mm (D) 0.07 mm
g. In
a double sampling plan N=1000, 
the maximum number of defectives that will permit the
acceptance of the lot on the basis of the two samples combined is
(A) 1 (B) 2
(C) 3 (D) 4
h. The probability of accepting product of some stated quality level is referred to as
(A) Producers risk. (B) Consumers risk.
(C) AQL. (D) Acceptance number
PART I
Answer any THREE Questions. Each question carries 14 marks.
Q.2 a.
Explain the hazard models used in
reliability theory. (7)
b. Define the terms reliability, availability
and maintainability. (7)
Q.3 a. Explain Weibull
distribution and its applications in reliability analysis. (7)
b. A
system consists of two identical independent units each with a constant failure
rate 
and mission time t=24
h. Compare the reliability of the system if they are placed in
(i) a series configuration (ii) a parallel configuration and (iii) a standby
configuration with perfect
switching. (7)
Q.4 a.
Discuss the problems of data collection for reliability design. (7)
b. How many components should be used in an active redundancy design to achieve a reliability of 0.999, such that for successful system operation a minimum of two components is required. Assume mission time = 720 h for a set of components that are identical and a failure rate of 0.00015/h. (7)
Q.5 a.
Define the term availability and
maintainability. On what factors do
these depend? (7)
b A system requires a reliability of 0.9 for ten hours of
operation. There are four units connected in series with unit failure rates
0.002, 0.003, 0.004 and 0.007 per hour. Allocate reliabilities to the four
units. (7)
Q.6 a. Discuss
the inherent value of reliability in electronic and telecommunication systems. (7)
b. Explain Markov methods for system structures. (7)
PART II
Answer any THREE Questions. Each question carries 14 marks.
Q.7 a.
Discuss the development of quality planning function. (7)
b. The number of defects found in 25 pieces of woollen goods are as follows:
3, 3, 6, 3, 0, 1, 3, 5, 7, 8, 4, 10, 5, 5, 5, 4, 3, 4, 5,1, 1, 0, 1, 1, 4
Compute
trial control limits. What value of standard number of defects would you suggest
for the period that follows. (7)
Q.8 a. Explain the following:
(i) O.C. curve of an ideal sampling plan. (4)
(ii) Conflicting interests of consumer and producer in the selection of sampling
plans. (3)
b.
A single sampling plan has N = 50, n =10 and c = 1. Using
hyper-geometric probabilities compute the probability of acceptance of a lot
with 2% defective. (7)
Q.9 a. Discuss the motivation and coordination for
quality. (7)
b. Give
the concept of quality circles. (7)
Q.10 a. Discuss the economical consideration in a
test plan selection for reliability and quality control. (7)
b. Describe in brief a sequential acceptance
test. (7)
Q.11 Write
short note on any TWO of the following:
(i) Quality rating.
(ii) Analysis of variance.
(iii) Design of experiments. (7 x 2 = 14)