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Chapter 30: Standard Data

Chapter 30: Standard Data. Reusing previously determined times to predict standard times for new operations. E.g., predict cost of automotive repairs Can be specialized for a particular industry, company, or process …. Advantages of Using Standard Data. Cost Time study is expensive.

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Chapter 30: Standard Data

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  1. Chapter 30: Standard Data • Reusing previously determined times to predict standard times for new operations. • E.g., predict cost of automotive repairs • Can be specialized for a particular industry, company, or process …

  2. Advantages of Using Standard Data • Cost • Time study is expensive. • Standard data allows you to use a table or an equation. • Ahead of Production • The operation does not have to be observed. • Allows estimates to be made for bids, method decisions, and scheduling. • Consistency • Values come from a bigger database. • Random errors tend to cancel over many studies. • Consistency is more important than accuracy.

  3. Random and Constant Errors

  4. Disadvantages of Standard Data • Imagining the Task • The analyst must be very familiar with the task. • Analysts may forget rarely done elements. • Database Cost • Developing the database costs money. • There are training and maintenance costs.

  5. Motions vs. Elements • Decision is about level of detail. • MTM times are at motion level. • An element system has a collection of individual motions. • Elements can come from an analysis, time studies, curve fitting, or a combination.

  6. Constant vs. Variable • Each element can be considered either constant or variable. • Constant elements either occur or don’t occur. • Constant elements tend to have large random error. • Variable elements depend on specifics of the situation. • Variable elements have smaller random error.

  7. Developing the Standard • Plan the work. • Classify the data. • Group the elements. • Analyze the job. • Develop the standard.

  8. Curve Fitting • To analyze experimental data: • Plot the data. • Guess several approximate curve shapes. • Use a computer to determine the constants for the shapes. • Select which equation you want to use.

  9. Statistical Concepts • Least-squares equation • Standard error • Coefficient of variation • Coefficient of determination • Coefficient of correlation • Residual

  10. Curve Shapes Y independent of X • Y = A • Determine that Y is independent of X by looking at the SE.

  11. 10 8 6 4 2 [y] y=4 0 2 4 6 8 10 [x] Y Independent of X • If Y is not related to X (is independent of X), then Y=A, where A is constant.

  12. Curve Shapes Y depends on X, 1 variable • Y = A + BX • Y = AXB • Y = AeBX • Y = A + BXn • Y = X / (A + BX) • Y = A + BX + CX2

  13. Straight Lines

  14. Geometric Curves

  15. Exponential Curves

  16. Hyperbolas

  17. Parabolas or Hyperbolas with a Third Constant

  18. Curve Shapes Y depends on X, multiple variables • Y = A + BX + CZ • Results in a family of curves

  19. Example Application: Walk Normal Times (min)

  20. First, plot the data

  21. Equations for Walking • NOTE: see attached Excel sheet intercept = ______ slope = _________ r2 = _______ σ = __________ • Therefore, Walk time is computed as: t = __________________ • So, if a new task is added that requires walking 7.4 m, how long should be allowed in the standard?

  22. Equations for Walk Data Set Walk time h = –.13 + .11 (loge Distance, m) r2 = .966 σ = .012 h 1/Walk time h = .24 – .96 (1/Distance, m) r2 = .881 σ = .021 h-1

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