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1 ISE Ch. 30 Ch. 30: Standard Data Means the reuse of previous times. For example, predict cost of automotive repairs.

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2 ISE Ch. 30 Advantages of Using Standard Data Ahead of Production The operation does not have to be observed. Allows estimates to be made for bids, method decisions, and scheduling. Cost Time study is expensive. Standard data allows you to use a table or an equation. Consistency Values come from a bigger database. Random errors tend to cancel over many studies. Consistency is more important than accuracy.

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3 ISE Ch. 30 Random and Constant Errors

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4 ISE Ch. 30 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.

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5 ISE Ch. 30 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.

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6 ISE Ch. 30 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.

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7 ISE Ch. 30 Developing the Standard Plan the work. Classify the data. Group the elements. Analyze the job. Develop the standard.

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8 ISE Ch. 30 Curve Fitting To analyze experimental data: 1. Plot the data. 2. Guess several approximate curve shapes. 3. Use a computer to determine the constants for the shapes. 4. Select which equation you want to use.

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9 ISE Ch. 30 Statistical Concepts Least-squares equation Standard error Coefficient of variation Coefficient of determination Coefficient of correlation Residual

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10 ISE Ch. 30 Curve Shapes Y independent of X Y = A Determine that Y is independent of X by looking at the SE [x] [y] y=4

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11 ISE Ch. 30 Curve Shapes Y depends on X, 1 variable Examples Others:

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12 ISE Ch. 30 Curve Shapes Y depends on X, multiple variables Y = A + BX + CZ Results in a family of curves

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13 ISE Ch. 30 Example Application: Walk Normal Times (min) 5 m10 m15 m20 m

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14 ISE Ch. 30 Walk Data Scatterplot

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15 ISE Ch. 30 Equations for Walk Data Set Walk time h = D r 2 =.986σ =.0073 h Walk time h = – D –.00013D 2 r 2 =.989σ =.0067 h Walk timeh = – (loge Distance, m) r 2 =.966σ =.012 h 1/Walk time h =.24 –.96 (1/D) r 2 =.881σ =.021 h -1

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