Two-factor Factorial Designs
Probability and Statistics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- For a levels of Factor A, b levels of Factor B, and n repetitions per cell:
- Montgomery, Douglas C., and George C. Runger, Applied Statistics and Probability for Engineers, 4 ed., New York: John Wiley and Sons, 2007.
- Source of Variation Mean Square F
- Randomized Complete Block ANOVA Table
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.
a concrete mix study crossing cement type with curing regime Given levels of factor A (a) = 5.0000; levels of factor B (b) = 4.0000; replicates per cell (n) = 3.0000, determine the total experimental runs (N) in runs.
Given
Find
total experimental runs (N), in runs
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except N is given, so isolate N 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: levels of factor A (a) = 5.0000, levels of factor B (b) = 4.0000, replicates per cell (n) = 3.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 60.0000 runs to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 120.0 — kept a factor of two that cancels in the correct rearrangement.
- 30.0000 — dropped that same factor in the other direction.
- 66.0000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
an asphalt study crossing binder grade with compaction effort Given total experimental runs (N) = 56.0000 runs; levels of factor A (a) = 5.0000; levels of factor B (b) = 2.0000, determine the replicates per cell (n).
Given
Find
replicates per cell (n)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except n is given, so isolate n 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n:
Step 3 — List the givens: total experimental runs (N) = 56.0000 runs, levels of factor A (a) = 5.0000, levels of factor B (b) = 2.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n = 5.6000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 11.2000 — kept a factor of two that cancels in the correct rearrangement.
- 2.8000 — dropped that same factor in the other direction.
- 6.1600 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a soil study crossing compaction energy with moisture level Given total experimental runs (N) = 140.0 runs; levels of factor A (a) = 4.0000; replicates per cell (n) = 5.0000, determine the levels of factor B (b).
Given
Find
levels of factor B (b)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except b is given, so isolate b 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for b:
Step 3 — List the givens: total experimental runs (N) = 140.0 runs, levels of factor A (a) = 4.0000, replicates per cell (n) = 5.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning b = 7.0000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 14.0000 — kept a factor of two that cancels in the correct rearrangement.
- 3.5000 — dropped that same factor in the other direction.
- 7.7000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a concrete mix study crossing cement type with curing regime Given levels of factor A (a) = 5.0000; levels of factor B (b) = 4.0000; replicates per cell (n) = 2.0000, determine the total experimental runs (N) in runs.
Given
Find
total experimental runs (N), in runs
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except N is given, so isolate N 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: levels of factor A (a) = 5.0000, levels of factor B (b) = 4.0000, replicates per cell (n) = 2.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 40.0000 runs to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 80.0000 — kept a factor of two that cancels in the correct rearrangement.
- 20.0000 — dropped that same factor in the other direction.
- 44.0000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
an asphalt study crossing binder grade with compaction effort Given total experimental runs (N) = 62.0000 runs; levels of factor A (a) = 4.0000; levels of factor B (b) = 2.0000, determine the replicates per cell (n).
Given
Find
replicates per cell (n)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except n is given, so isolate n 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n:
Step 3 — List the givens: total experimental runs (N) = 62.0000 runs, levels of factor A (a) = 4.0000, levels of factor B (b) = 2.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n = 7.7500 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 15.5000 — kept a factor of two that cancels in the correct rearrangement.
- 3.8750 — dropped that same factor in the other direction.
- 8.5250 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a soil study crossing compaction energy with moisture level Given total experimental runs (N) = 120.0 runs; levels of factor A (a) = 2.0000; replicates per cell (n) = 2.0000, determine the levels of factor B (b).
Given
Find
levels of factor B (b)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except b is given, so isolate b 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for b:
Step 3 — List the givens: total experimental runs (N) = 120.0 runs, levels of factor A (a) = 2.0000, replicates per cell (n) = 2.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning b = 30.0000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 60.0000 — kept a factor of two that cancels in the correct rearrangement.
- 15.0000 — dropped that same factor in the other direction.
- 33.0000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a concrete mix study crossing cement type with curing regime Given levels of factor A (a) = 3.0000; levels of factor B (b) = 4.0000; replicates per cell (n) = 4.0000, determine the total experimental runs (N) in runs.
Given
Find
total experimental runs (N), in runs
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except N is given, so isolate N 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: levels of factor A (a) = 3.0000, levels of factor B (b) = 4.0000, replicates per cell (n) = 4.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 48.0000 runs to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 96.0000 — kept a factor of two that cancels in the correct rearrangement.
- 24.0000 — dropped that same factor in the other direction.
- 52.8000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
an asphalt study crossing binder grade with compaction effort Given total experimental runs (N) = 178.0 runs; levels of factor A (a) = 3.0000; levels of factor B (b) = 3.0000, determine the replicates per cell (n).
Given
Find
replicates per cell (n)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except n is given, so isolate n 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n:
Step 3 — List the givens: total experimental runs (N) = 178.0 runs, levels of factor A (a) = 3.0000, levels of factor B (b) = 3.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n = 19.7778 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 39.5556 — kept a factor of two that cancels in the correct rearrangement.
- 9.8889 — dropped that same factor in the other direction.
- 21.7556 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a soil study crossing compaction energy with moisture level Given total experimental runs (N) = 136.0 runs; levels of factor A (a) = 5.0000; replicates per cell (n) = 2.0000, determine the levels of factor B (b).
Given
Find
levels of factor B (b)
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except b is given, so isolate b 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for b:
Step 3 — List the givens: total experimental runs (N) = 136.0 runs, levels of factor A (a) = 5.0000, replicates per cell (n) = 2.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning b = 13.6000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 27.2000 — kept a factor of two that cancels in the correct rearrangement.
- 6.8000 — dropped that same factor in the other direction.
- 14.9600 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs
a concrete mix study crossing cement type with curing regime Given levels of factor A (a) = 4.0000; levels of factor B (b) = 5.0000; replicates per cell (n) = 5.0000, determine the total experimental runs (N) in runs.
Given
Find
total experimental runs (N), in runs
Start with the thinking
- The governing relation printed in this handbook section is Runs in a two-factor factorial design.
- Everything except N is given, so isolate N 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.
- A two-factor factorial design tests every level combination of two factors with n replicates per cell.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: levels of factor A (a) = 4.0000, levels of factor B (b) = 5.0000, replicates per cell (n) = 5.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 100.0 runs to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 200.0 — kept a factor of two that cancels in the correct rearrangement.
- 50.0000 — dropped that same factor in the other direction.
- 110.0 — rounded an intermediate value before the final step.
Reference: FE Handbook — Two-factor Factorial Designs