QM0021-Statistical Process Control

FALL-2015
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MBA Semester 3
QM0021-Statistical Process Control
(Book ID: B1725)
Assignment (60 Marks)
Note: Answer all questions must be written within 300 to 400 words each. Each Question carries 10
marks 6 X 10=60.
Q1. (a) What are the two main causes of variation? Explain.
(b) Define the term ‘process’. Give an example of process.
Answer. a. Common and special causes are the two distinct origins of variation in a process, as defined in
the statistical thinking and methods of Walter A. Shewhart and W. Edwards Deming. Briefly, "common
causes", also called Natural patterns, are the usual, historical, quantifiable variation in a system, while
"special causes" are unusual, not previously observed, non-quantifiable variation.
In manufacturing, quality is defined
Q2. (a) What is meant by Standard Deviation?
(b) Calculate the standard deviation of the following data, which represents the number of defective
products by a machine: 4, 2, 5, 8 and 6.
Answer. a. Standard deviation: In statistics, the standard deviation (SD, also represented by the Greek
letter sigma σ or s) is a measure that is used to quantify the amount of variation or dispersion of a set of
data values. A standard deviation close to 0 indicates that the data points tend to be very close to the
mean (also called the expected value) of the set, while a high standard deviation indicates that the data
points are spread out over a wider
Q3. a) Give the meaning of the following basic terminologies in Probability:
i) Sample Space
ii) Mutually Exclusive events
b) Mention the properties of probability.
c) Define the term ‘random variable’.
Answer. a. In probability theory, the sample space of an experiment or random trial is the set of all
possible outcomes or results of that experiment. A sample space is usually denoted using set notation, and
the possible outcomes are listed as elements in the set. It is common to refer to a sample space by the
labels S, Ω, or U (for "universal set").
For example, if the experiment is tossing a coin, the sample space is typically the set {head, tail}. For
tossing two coins, the
Q4. (a) Differentiate between accuracy and precision.
(b) Write a brief note on ‘Funnel Experiment’.
Answer.
Accuracy is defined as, "The ability of a measurement to match the actual value of the quantity being
measured". If in reality it is 34.0 F outside and a temperature sensor reads 34.0 F, then than sensor is
accurate.
Precision is defined as,
(1) The ability of a measurement to be consistently reproduced.
(2) The number of significant
Q5. Define the terms: ‘process capability’ and ‘process stability’. Explain Cp index and Cpk index.
Answer. Process Stability refers to the consistency of the process with respect to important process
characteristics such as the average value of a key dimension or the variation in that key dimension. If the
process behaves consistently over time, then we say that the process is stable or in control. The graphic
below illustrates a stable process. The process
Q6. Give the meaning of the following:
i) Hypothesis testing
ii) Control chart
iii) Experimental design
iv) Acceptance Sampling
Answer. i) Hypothesis testing: A statistical hypothesis is a hypothesis that is testable on the basis of
observing a process that is modeled via a set of random variables.A statistical hypothesis test is a method
of statistical inference. Commonly, two statistical data sets are compared, or a data set obtained by
sampling is compared against a synthetic data set from an idealized model. A hypothesis is proposed for
the statistical relationship between the two
FALL-2015
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08894344452