Test Statistics
Probability and Statistics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- The Z score is applicable when the standard deviation (s) is known. The test statistic is applicable when the standard deviation
- Engineering Probability and Statistics
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 a test statistic to compare a small sample mean to a target value. Given sample mean (xbar) = 98.9000; hypothesized mean (mu0) = 91.7000; sample std dev (s) = 3.4000; sample size (n) = 22.0000, determine the test statistic (t).
Given
Find
test statistic (t)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except t is given, so isolate t 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for t:
Step 3 — List the givens: sample mean (xbar) = 98.9000, hypothesized mean (mu0) = 91.7000, sample std dev (s) = 3.4000, sample size (n) = 22.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning t = 9.9326 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 19.8653 — kept a factor of two that cancels in the correct rearrangement.
- 4.9663 — dropped that same factor in the other direction.
- 10.9259 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
A student calculates the t test statistic for a lab measurement series. Given hypothesized mean (mu0) = 92.5000; sample std dev (s) = 3.3000; sample size (n) = 11.0000; test statistic (t) = 6.3900, determine the sample mean (xbar).
Given
Find
sample mean (xbar)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except xbar is given, so isolate xbar 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for xbar:
Step 3 — List the givens: hypothesized mean (mu0) = 92.5000, sample std dev (s) = 3.3000, sample size (n) = 11.0000, test statistic (t) = 6.3900.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning xbar = 98.8580 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 197.7 — kept a factor of two that cancels in the correct rearrangement.
- 49.4290 — dropped that same factor in the other direction.
- 108.7 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
The test statistic exceeds the critical value, leading to rejection of the null hypothesis. Given sample mean (xbar) = 104.8; hypothesized mean (mu0) = 98.1000; sample size (n) = 23.0000; test statistic (t) = 5.0500, determine the sample std dev (s).
Given
Find
sample std dev (s)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except s is given, so isolate s 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for s:
Step 3 — List the givens: sample mean (xbar) = 104.8, hypothesized mean (mu0) = 98.1000, sample size (n) = 23.0000, test statistic (t) = 5.0500.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning s = 6.3628 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 12.7256 — kept a factor of two that cancels in the correct rearrangement.
- 3.1814 — dropped that same factor in the other direction.
- 6.9991 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
An engineer computes a test statistic to compare a small sample mean to a target value. Given sample mean (xbar) = 107.0; hypothesized mean (mu0) = 95.2000; sample std dev (s) = 2.1000; sample size (n) = 6.0000, determine the test statistic (t).
Given
Find
test statistic (t)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except t is given, so isolate t 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for t:
Step 3 — List the givens: sample mean (xbar) = 107.0, hypothesized mean (mu0) = 95.2000, sample std dev (s) = 2.1000, sample size (n) = 6.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning t = 13.7638 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 27.5276 — kept a factor of two that cancels in the correct rearrangement.
- 6.8819 — dropped that same factor in the other direction.
- 15.1402 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
A student calculates the t test statistic for a lab measurement series. Given hypothesized mean (mu0) = 95.8000; sample std dev (s) = 8.5000; sample size (n) = 19.0000; test statistic (t) = 3.6900, determine the sample mean (xbar).
Given
Find
sample mean (xbar)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except xbar is given, so isolate xbar 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for xbar:
Step 3 — List the givens: hypothesized mean (mu0) = 95.8000, sample std dev (s) = 8.5000, sample size (n) = 19.0000, test statistic (t) = 3.6900.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning xbar = 103.0 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 206.0 — kept a factor of two that cancels in the correct rearrangement.
- 51.4978 — dropped that same factor in the other direction.
- 113.3 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
The test statistic exceeds the critical value, leading to rejection of the null hypothesis. Given sample mean (xbar) = 98.5000; hypothesized mean (mu0) = 96.2000; sample size (n) = 30.0000; test statistic (t) = 4.2100, determine the sample std dev (s).
Given
Find
sample std dev (s)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except s is given, so isolate s 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for s:
Step 3 — List the givens: sample mean (xbar) = 98.5000, hypothesized mean (mu0) = 96.2000, sample size (n) = 30.0000, test statistic (t) = 4.2100.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning s = 2.9923 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 5.9846 — kept a factor of two that cancels in the correct rearrangement.
- 1.4962 — dropped that same factor in the other direction.
- 3.2915 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
An engineer computes a test statistic to compare a small sample mean to a target value. Given sample mean (xbar) = 104.9; hypothesized mean (mu0) = 95.4000; sample std dev (s) = 7.3000; sample size (n) = 27.0000, determine the test statistic (t).
Given
Find
test statistic (t)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except t is given, so isolate t 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for t:
Step 3 — List the givens: sample mean (xbar) = 104.9, hypothesized mean (mu0) = 95.4000, sample std dev (s) = 7.3000, sample size (n) = 27.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning t = 6.7621 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 13.5242 — kept a factor of two that cancels in the correct rearrangement.
- 3.3811 — dropped that same factor in the other direction.
- 7.4383 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
A student calculates the t test statistic for a lab measurement series. Given hypothesized mean (mu0) = 99.4000; sample std dev (s) = 3.1000; sample size (n) = 20.0000; test statistic (t) = -3.1900, determine the sample mean (xbar).
Given
Find
sample mean (xbar)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except xbar is given, so isolate xbar 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for xbar:
Step 3 — List the givens: hypothesized mean (mu0) = 99.4000, sample std dev (s) = 3.1000, sample size (n) = 20.0000, test statistic (t) = -3.1900.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning xbar = 97.1888 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 194.4 — kept a factor of two that cancels in the correct rearrangement.
- 48.5944 — dropped that same factor in the other direction.
- 106.9 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
The test statistic exceeds the critical value, leading to rejection of the null hypothesis. Given sample mean (xbar) = 96.0000; hypothesized mean (mu0) = 94.6000; sample size (n) = 17.0000; test statistic (t) = -3.0800, determine the sample std dev (s).
Given
Find
sample std dev (s)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except s is given, so isolate s 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for s:
Step 3 — List the givens: sample mean (xbar) = 96.0000, hypothesized mean (mu0) = 94.6000, sample size (n) = 17.0000, test statistic (t) = -3.0800.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning s = -1.8741 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -3.7483 — kept a factor of two that cancels in the correct rearrangement.
- -0.9371 — dropped that same factor in the other direction.
- -2.0616 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics
An engineer computes a test statistic to compare a small sample mean to a target value. Given sample mean (xbar) = 96.1000; hypothesized mean (mu0) = 96.4000; sample std dev (s) = 2.3000; sample size (n) = 26.0000, determine the test statistic (t).
Given
Find
test statistic (t)
Start with the thinking
- The governing relation printed in this handbook section is Test statistic — Student's t.
- Everything except t is given, so isolate t 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.
- This test statistic follows Student's t distribution for small-sample hypothesis testing.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for t:
Step 3 — List the givens: sample mean (xbar) = 96.1000, hypothesized mean (mu0) = 96.4000, sample std dev (s) = 2.3000, sample size (n) = 26.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning t = -0.6651 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -1.3302 — kept a factor of two that cancels in the correct rearrangement.
- -0.3325 — dropped that same factor in the other direction.
- -0.7316 — rounded an intermediate value before the final step.
Reference: FE Handbook — Test Statistics