Residual
Probability and Statistics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Confidence Interval for Intercept (â):
- Engineering Probability and Statistics
- Confidence Interval for Slope (b̂):
- Sample Correlation Coefficient (R) and Coefficient of Determination (R2):
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
An engineer computes the residual between a measured and predicted strength. Given observed value (yi) = 91.4000; predicted value (yhat) = 69.6000, determine the residual (e).
Given
Find
residual (e)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except e is given, so isolate e symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for e:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning e = 21.8000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 43.6000 — kept a factor of two that cancels in the correct rearrangement.
- 10.9000 — dropped that same factor in the other direction.
- 23.9800 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A student checks the residual of a data point on a least squares line. Given predicted value (yhat) = 64.2000; residual (e) = 4.9800, determine the observed value (yi).
Given
Find
observed value (yi)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yi is given, so isolate yi symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yi:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yi = 69.1800 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 138.4 — kept a factor of two that cancels in the correct rearrangement.
- 34.5900 — dropped that same factor in the other direction.
- 76.0980 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A large residual flags an outlier in the calibration data set. Given observed value (yi) = 94.9000; residual (e) = -7.6500, determine the predicted value (yhat).
Given
Find
predicted value (yhat)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yhat is given, so isolate yhat symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yhat:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yhat = 102.6 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 205.1 — kept a factor of two that cancels in the correct rearrangement.
- 51.2750 — dropped that same factor in the other direction.
- 112.8 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
An engineer computes the residual between a measured and predicted strength. Given observed value (yi) = 47.5000; predicted value (yhat) = 47.7000, determine the residual (e).
Given
Find
residual (e)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except e is given, so isolate e symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for e:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning e = -0.2000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -0.4000 — kept a factor of two that cancels in the correct rearrangement.
- -0.1000 — dropped that same factor in the other direction.
- -0.2200 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A student checks the residual of a data point on a least squares line. Given predicted value (yhat) = 49.6000; residual (e) = -9.1400, determine the observed value (yi).
Given
Find
observed value (yi)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yi is given, so isolate yi symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yi:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yi = 40.4600 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 80.9200 — kept a factor of two that cancels in the correct rearrangement.
- 20.2300 — dropped that same factor in the other direction.
- 44.5060 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A large residual flags an outlier in the calibration data set. Given observed value (yi) = 30.0000; residual (e) = -8.0200, determine the predicted value (yhat).
Given
Find
predicted value (yhat)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yhat is given, so isolate yhat symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yhat:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yhat = 38.0200 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 76.0400 — kept a factor of two that cancels in the correct rearrangement.
- 19.0100 — dropped that same factor in the other direction.
- 41.8220 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
An engineer computes the residual between a measured and predicted strength. Given observed value (yi) = 11.1000; predicted value (yhat) = 39.9000, determine the residual (e).
Given
Find
residual (e)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except e is given, so isolate e symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for e:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning e = -28.8000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -57.6000 — kept a factor of two that cancels in the correct rearrangement.
- -14.4000 — dropped that same factor in the other direction.
- -31.6800 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A student checks the residual of a data point on a least squares line. Given predicted value (yhat) = 22.9000; residual (e) = 0.6900, determine the observed value (yi).
Given
Find
observed value (yi)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yi is given, so isolate yi symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yi:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yi = 23.5900 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 47.1800 — kept a factor of two that cancels in the correct rearrangement.
- 11.7950 — dropped that same factor in the other direction.
- 25.9490 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
A large residual flags an outlier in the calibration data set. Given observed value (yi) = 44.9000; residual (e) = -16.5500, determine the predicted value (yhat).
Given
Find
predicted value (yhat)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except yhat is given, so isolate yhat symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for yhat:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning yhat = 61.4500 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 122.9 — kept a factor of two that cancels in the correct rearrangement.
- 30.7250 — dropped that same factor in the other direction.
- 67.5950 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual
An engineer computes the residual between a measured and predicted strength. Given observed value (yi) = 96.0000; predicted value (yhat) = 32.5000, determine the residual (e).
Given
Find
residual (e)
Start with the thinking
- The governing relation printed in this handbook section is Residual of a regression fit.
- Everything except e is given, so isolate e symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The residual is the difference between an observed value and the value predicted by the regression model.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for e:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning e = 63.5000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 127.0 — kept a factor of two that cancels in the correct rearrangement.
- 31.7500 — dropped that same factor in the other direction.
- 69.8500 — rounded an intermediate value before the final step.
Reference: FE Handbook — Residual