STAT 20223: Statistical Process Control
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Questions and Answers

What type of data is often used in attribute control charts?

  • Continuous data
  • Discrete data (correct)
  • Qualitative data
  • Ordinal data

    • Which of the following is NOT a type of attribute control chart based on the Binomial Distribution?

  • u chart (correct)
  • c chart
  • np chart
  • p chart

    • What is the main purpose of using a p chart?

  • To monitor the standard deviation of a process
  • To monitor the range of a process
  • To monitor the mean of a process
  • To monitor the proportion of defective items (correct)

    • Which of the following attribute control charts is based on the Poisson Distribution?

    <p>u chart and c chart</p> Signup and view all the answers

    What type of distribution is used to create the np chart?

    <p>Binomial Distribution</p> Signup and view all the answers

    What is the primary use of attribute control charts?

    <p>To evaluate variation in a process</p> Signup and view all the answers

    Which of the following is a characteristic of attribute control charts?

    <p>They are used with discrete or count data</p> Signup and view all the answers

    How many main types of attribute control charts are there?

    <p>Two</p> Signup and view all the answers

    What is the primary concern of the supervisor at the small hospital in the illustrative example?

    <p>Keeping the number of errors in the medical records in control</p> Signup and view all the answers

    What type of chart is used to monitor the proportion of defective items produced by a process?

    <p>Laney P' chart</p> Signup and view all the answers

    What is the effect of overdispersion on a traditional P chart?

    <p>It shows an increased number of points outside the control limits</p> Signup and view all the answers

    What is the purpose of using a Laney P' chart in the radiology department example?

    <p>To monitor the proportion of patients requiring a retest due to imaging errors</p> Signup and view all the answers

    What is the average subgroup size in the illustrative example?

    <p>More than 2,500</p> Signup and view all the answers

    What is the effect of underdispersion on a traditional P chart?

    <p>It shows too few points outside the control limits</p> Signup and view all the answers

    What is the name of the chart used in the illustrative example?

    <p>P chart diagnostic</p> Signup and view all the answers

    What is the purpose of the P chart diagnostic test in the illustrative example?

    <p>To test for overdispersion</p> Signup and view all the answers

    What is the purpose of using a U Chart in quality control?

    <p>To monitor the number of defects per unit</p> Signup and view all the answers

    What is the formula for the probability of x occurrences in a specified time or space?

    <p>𝑃(𝑋 = 𝑥) = 𝑒^𝜆 * 𝜆^𝑥 / 𝑥!</p> Signup and view all the answers

    What is the purpose of using Tests 1 and 2 in establishing control limits?

    <p>To detect instabilities in a process</p> Signup and view all the answers

    What is the range of the variable X in the probability formula?

    <p>X can equal any nonnegative integer</p> Signup and view all the answers

    What is the purpose of using an NP Chart?

    <p>To monitor process stability over time</p> Signup and view all the answers

    What is the significance of 𝜆 in the probability formula?

    <p>The average number of occurrences over a specified time or space</p> Signup and view all the answers

    What type of control chart is used to monitor the number of defective items that can be classified into two categories?

    <p>NP chart</p> Signup and view all the answers

    What kind of data would require the use of a Laney P' chart?

    <p>Data with high average and overdispersion</p> Signup and view all the answers

    What is the primary purpose of using a control chart?

    <p>To monitor process stability over time</p> Signup and view all the answers

    What is the benefit of using an NP chart in a delivery service?

    <p>To monitor the number of delivery vehicles that are out of service</p> Signup and view all the answers

    What is an advantage of using a Laney P' chart over a traditional P chart?

    <p>It is more suitable for data with overdispersion</p> Signup and view all the answers

    What is the purpose of creating an NP chart in the illustrative example?

    <p>To monitor the number of light bulbs that do not light</p> Signup and view all the answers

    In which menu can you find the option to create a Laney P' chart?

    <p>Stat &gt; Control Charts &gt; Attributes Charts &gt; Laney P'</p> Signup and view all the answers

    How many light bulbs are tested each hour in the illustrative example?

    <p>500</p> Signup and view all the answers

    What is the formula for the average number of nonconformities per inspection unit?

    <p>x / n</p> Signup and view all the answers

    What is the distribution of the variable x in the U chart?

    <p>Poisson distribution</p> Signup and view all the answers

    What is the formula for the variance of the average number of nonconformities per inspection unit (u)?

    <p>λ / n</p> Signup and view all the answers

    What is the purpose of the U chart in the illustrative example?

    <p>To monitor the average number of defects per set of pages</p> Signup and view all the answers

    What is the input variable in the U chart for the illustrative example?

    <p>Errors</p> Signup and view all the answers

    What is the subgroup size in the U chart for the illustrative example?

    <p>Number of Pages</p> Signup and view all the answers

    What is the parameter of the Poisson distribution in the U chart?

    <p>λ</p> Signup and view all the answers

    What is the formula for the mean of the average number of nonconformities per inspection unit (u)?

    <p>λ</p> Signup and view all the answers

    Study Notes

    STATISTICAL PROCESS CONTROL

    • Statistical process control is used to evaluate variation in a process where the measurement is an attribute (i.e., discrete or count data).

    ATTRIBUTE CONTROL CHARTS

    • Attribute control charts are used to monitor the proportion of defective items or the number of defects per unit.
    • There are two main types of attribute control charts based on:
      • Binomial Distribution: p chart and np chart
      • Poisson Distribution: u chart and c chart

    P CHART

    • A p chart is used to monitor the proportion of defective items where each item can be classified into one of two categories (e.g., pass or fail).
    • It is used to monitor process stability over time and identify instabilities.

    LANEY P' CHART

    • A Laney P' chart is used to monitor the proportion of defective items and adjust for overdispersion or underdispersion in the data.
    • It is used when the data exhibit overdispersion or underdispersion, causing a traditional P chart to show an increased number of points outside the control limits or too few points outside the control limits.

    NP CHART

    • An NP chart is used to monitor the number of defective items where each item can be classified into one of two categories (e.g., pass or fail).
    • It is used to monitor process stability over time and identify instabilities.

    U CHART

    • A U chart is used to monitor the number of defects per unit, where each item can have multiple defects.
    • It is used to monitor process stability over time and identify instabilities.
    • The probability formula for a U chart is based on the Poisson distribution: 𝑒 −λ λ 𝑥 / 𝑥!
    • The average number of nonconformities per inspection unit is 𝑢 = 𝑥 / 𝑛, where 𝑥 is the total number of nonconformities and 𝑛 is the number of inspection units.

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    Quiz Team

    Description

    This quiz covers statistical process control, attribute control charts, and capability analysis. It is a part of the STAT 20223 course.

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