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IENG 217 Cost Estimating for Engineers

IENG 217 Cost Estimating for Engineers. Estimating. Nature of the estimate. Timeliness Purpose Accuracy Effort Accountability. Universal Methods. Opinion Guesstimating, TLAR Conference Delphi, Sales Force Composite, Exec. Dec. Comparison C c (D c ) < C a (D a ) < C b (D b )

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IENG 217 Cost Estimating for Engineers

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  1. IENG 217Cost Estimating for Engineers Estimating

  2. Nature of the estimate • Timeliness • Purpose • Accuracy • Effort • Accountability

  3. Universal Methods • Opinion • Guesstimating, TLAR • Conference • Delphi, Sales Force Composite, Exec. Dec. • Comparison • Cc(Dc) < Ca(Da) < Cb(Db) • Unit

  4. Comparison

  5. Unit

  6. Unit • Metal machining cost may be related to length of the bar stock that is turned on a lathe. Actual tickets yield

  7. Unit • Metal machining cost may be related to length of the bar stock that is turned on a lathe. Actual tickets yield Ca = 110/9 = $12.22 / in.

  8. Unit Cost • Fails to apply principle of economy of scale • Accounts for slope only • Regression: Ca = -23.3 + 20(length)

  9. Operational Methods • Cost estimating relationships • Time estimating relationships • Performance time data

  10. Cost Estimating Relationships • Parameters Ca = -23.3 + 20(length) bar stock length ( 5 inches ) used in CER ( $76.70 ) is often called a parameter – it is not CER is actually a parametric equation

  11. Cost Estimating Relationship

  12. Cost Estimating Relationship • Typical arc welder draws 200 amps for a 20 volt arc welding process. If we have a 10 in/min welding travel speed and a 95% machine efficiency, estimate the cost per foot of a weld if the utility costs are $0.08 per KWhr.

  13. Cost Estimating Relationship • WWII military aircraft constructed of aluminum (regression; 10 contractors)

  14. Performance Time Data • Time Study • Work Sampling

  15. Performance Time Data Alg. • Collected several measurements from ops. • Classify elements into common group • Regress element time against one or more independent causal variables • Determine if TER is constant or variable • If TER is constant, determine value • If TER is variable, convert to time table or eq. • Collect all constant variable elements for operation • If accuracy is acceptable, use information for estimating designs

  16. Constant or Variable ? • 5 time measurements taken on a manual handling task Weight, lb. 1 3 4 5 7 Time, min. .15 .20 .30 .40 .50 Regression yields

  17. Constant or Variable ? • Test 1 • Test 2

  18. Constant or Variable ? • 5 time measurements taken on a manual handling task (test 1, P1 = 100%) Weight, lb. 1 3 4 5 7 Time, min. .15 .20 .30 .40 .50 yhat .1225 .4975

  19. Carriage / Support Assembly

  20. Carriage / Support Assembly

  21. Carriage / Support Assembly

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