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Question

Statement - I : $\bar{X}$-chart, np-chart and R-chart are the techniques used for product control under Statistical Quality Control.
Statement - II : Operating characteristic curve helps determine whether a particular acceptance sampling plan meets both the product's and the consumer's risk requirements.

The correct answer is
Statement - I is incorrect while Statement - II correct.

To evaluate the statements provided, we need to delve into Statistical Quality Control (SQC) and the use of Operating Characteristic (OC) curves. Let's inspect each statement individually for their validity:

  1. Statement - I: “\(\bar{X}\)-chart, np-chart and R-chart are the techniques used for product control under Statistical Quality Control.”

SQC is a method used for monitoring and controlling a process to ensure that it operates at its full potential. It primarily uses control charts like \(\bar{X}\)-chart, R-chart, and others to monitor product-related and process-related characteristics.

  • \(\bar{X}\)-chart: Used for controlling the process mean.
  • R-chart: Used for controlling process variability (range).
  • np-chart: Used for controlling the number of defective items in a sample, which is under attribute control charts, not product control per se.

These charts are primarily used for process control, not specifically for product control, thus making Statement I inaccurate.

  1. Statement - II: “Operating characteristic curve helps determine whether a particular acceptance sampling plan meets both the product's and the consumer's risk requirements.”

An Operating Characteristic (OC) curve is indeed a graphical representation in acceptance sampling used to show the probability of accepting a batch of goods given the proportion of defective items. This curve allows you to see how the sampling plan protects both the producer (i.e., the producer's risk of rejecting a good batch) and the consumer (i.e., the consumer's risk of accepting a bad batch).

Therefore, Statement II accurately describes the use of OC curves in quality control.

Given the analysis above, the correct assessment of the statements is:

  • Statement - I is incorrect while Statement - II is correct.
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Important Questions from Quality Control - Teaching

  1. A system has 99.99% uptime and has a mean-time-between-failure of 1 day. How fast does the system has to repair itself in order to reach this availability goal?

  2. An X̅ chart uses the following data

  3. The probability law used for calculating the control limits of 'P' chart is

  4. Which of the following is a part of internal compliance monitoring?
  5. Some tools needed for problem solving are :
    (a) Pareto chart
    (b) Check sheet
    (c) Profit and loss statement
    (d) Cause and effect diagram
    (e) Standardized recipes
    (f) Process chart
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