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LESSON 012 · REPLICATION
When a Result Has to Survive Another Try
An experiment produces an interesting result. Is that the beginning of knowledge—or the beginning of a second experiment? Explore what changes when a finding is tested again with new observations.
FREE · BEGINNER · 40–50 MINUTES · NO ENROLLMENT · OCTOBER 31, 2026
What you need: paper or a notes app, pencil, and a calculator if useful. The mini-lab is entirely paper-based; a physical experiment is optional.
Previously: Lesson 011 — Correlation & Causation.

A finding becomes a question for the next investigator
In Lesson 011, our imaginary paper-airplane comparison found that Design B traveled farther on average than Design A. But the comparison contained only five throws per design, and the figures were invented for teaching. Before turning that difference into a confident generalization, we need to ask what happens when the question is tested again.
A good investigation leaves enough of a trail that another learner can check the arithmetic, understand the methods, and gather fresh observations. These are related but different acts. Our aim is not to defend an exciting first answer at all costs. It is to find out how well the answer survives scrutiny.
Learning objectives
- Distinguish computational reproducibility, replicability, and generalizability.
- Explain why one small sample cannot establish a universal claim.
- Recalculate a comparison using newly invented observations.
- Write a test procedure clear enough for another investigator to follow.
- Identify ordinary reasons that a new result may differ from an earlier one.
- State a revised conclusion without overstating what was demonstrated.
1. Two kinds of returning
The National Academies of Sciences, Engineering, and Medicine use these specific definitions in their 2019 report Reproducibility and Replicability in Science:
Terms that should not be confused
Computational reproducibility: Using the same input data, code, analytical procedures, and conditions to obtain consistent computational results. Recalculating an existing data table is a small classroom analogy.
Replicability: Collecting new data to address the same scientific question and assessing whether the new findings are consistent with earlier findings, considering uncertainty.
Generalizability: Asking whether a finding applies to different people, places, materials, or settings beyond those originally studied.
Disciplines sometimes use these words differently, so good communication specifies the intended meaning. Reproducing a calculation is not the same as independently repeating an experiment. Replication does not require exactly matching every measured value.
2. Why a result may change when you try again
Repeated studies may differ because of ordinary sampling variability, measurement error, differences in procedure, changing conditions, publication biases, incomplete descriptions, or a mistaken causal model. Disagreement can expose a limitation in the original study, but it does not automatically establish dishonesty or misconduct.
Likewise, a consistent numerical result does not guarantee that the original analysis was correct; repeating the same faulty calculation can reproduce the same mistake.
Ask these before judging a second result
- Were the scientific questions truly comparable?
- Did the investigators use new observations or only recalculate the old ones?
- Were materials, conditions, and outcomes defined the same way?
- How much variation would be ordinary at this sample size?
- Could the result depend on an unrecognized condition?
The National Academies report explains why both transparency and the interpretation of replication attempts matter.
3. Mini-lab · Return to the paper airplanes
15–20 MINUTES · PAPER ONLY · ALL DATA INVENTED
In Lesson 011 we compared two hypothetical airplane designs. We now imagine a second round with five new throws per design. The numbers below are invented classroom measurements, not an experiment we actually performed.
| Round (5 throws/design) | Design A mean | Design B mean | B − A |
|---|---|---|---|
| First five throws | 3.12 m | 3.30 m | +0.18 m |
| Second five throws | 3.28 m | 3.14 m | −0.14 m |
| Combined ten throws | 3.20 m | 3.22 m | +0.02 m |
The first round gives B a 0.18-meter lead. The second gives A a 0.14-meter lead. When both equally sized rounds are combined, B leads by only 0.02 meters. This is not proof that the designs are equivalent—or that B really has a positive causal effect. The samples are small and we have not estimated uncertainty.
Try the calculations yourself
- Subtract the mean of A from the mean of B in the first round.
- Repeat for the second round, noting the change in sign.
- Calculate the combined mean for each design. Because each round contains five throws, average the two round means equally.
- Compare the combined difference with the original difference.
- Write one sentence describing the pattern and one stating what remains uncertain.
Answer guide
First round: 3.30 − 3.12 = +0.18 m (B higher).
Second round: 3.14 − 3.28 = −0.14 m (A higher).
Combined A: (3.12 + 3.28) / 2 = 3.20 m.
Combined B: (3.30 + 3.14) / 2 = 3.22 m.
Combined difference: 3.22 − 3.20 = +0.02 m.
Interpretation: The observed difference changed across rounds. A small, variable sample is insufficient to conclude that either design is reliably superior.
4. Reproduce the numbers from individual observations
A transparent investigation lets another reader verify the arithmetic, rather than trusting only a summary table. Below is one possible set of invented second-round measurements that produces the displayed averages:
| Design | Second-round distances (meters) | Sum | Mean |
|---|---|---|---|
| A | 3.2, 3.3, 3.4, 3.1, 3.4 | 16.4 | 3.28 |
| B | 3.0, 3.1, 3.2, 3.1, 3.3 | 15.7 | 3.14 |
Add the five values for each row and divide by five. A classmate who can obtain the same means from these same invented values has reproduced the computation in a small educational sense. They have not collected new flight data, so they have not independently replicated the experiment.
5. Write a procedure someone else could actually follow
An instruction such as “throw a paper airplane normally” leaves many critical decisions unstated. An independent tester needs enough detail to understand how the experiment was conducted without guessing.
Build a repeatable protocol
- Materials: Specify paper size, weight, folding diagrams, and how each design differs.
- Setting: State launch position, clear indoor space, and conditions such as strong air movement.
- Trial order: Decide whether A or B goes first in each pair using a coin or another documented method.
- Outcome: Define whether distance ends at first contact with the ground or final stopping place.
- Recording: Keep every attempt, including failed launches and unexpected results, with a predeclared rule for handling unusable trials.
- Analysis: Decide in advance what mean, spread, and comparison will be reported.
Safety matters more than experimental neatness: use a harmless paper model in an uncluttered space. If physical testing is inconvenient, remain with the paper exercise.
6. A new result is not a demand for an identical number
Every measurement comes with variation and limits. In many scientific settings, consistent replication means findings are compatible given their uncertainty, not that all results match to the last decimal place.
When results disagree, check the research questions, measurements, procedures, statistical uncertainty, and possible conditions on which an effect depends. A result that holds in one environment and not another may identify an important boundary condition, not merely a failed investigation.
With our two five-throw samples, we have not calculated a standard deviation, confidence interval, or statistical model of the difference. We should therefore avoid claiming demonstrated superiority or demonstrated equivalence.
7. Replication, publication, and intellectual continuity
Publishing a finding makes it available for scrutiny; it does not make it permanent truth. Good research records its steps clearly and welcomes independent assessment. A stronger conclusion may emerge from confirmation, careful qualification, or recognition that the first estimate was unstable.
For Nova Academy, this becomes a learning principle: the continuity of inquiry lives in the question, the method, and the record—even when the answer changes. This is an educational and philosophical interpretation, not a separate experimental law.
The Quantum Atrium provides a neighboring pathway into deeper research and source-based exploration as the Academy expands.
8. Field note · Ask a second investigator
A small challenge with a partner—or on your own
- Choose a low-stakes claim that can be tested without collecting private data.
- Write a one-paragraph procedure so another reader can understand the steps.
- Specify exactly what new observations would count as a second attempt.
- Describe what range of outcomes would make you more confident, less confident, or eager to investigate further.
- Finish with the sentence: “I would trust this result more if…”
Do not assume a second attempt must agree with the first. Ask what the disagreement teaches about the method, the setting, and the original claim.
9. Knowledge check · Six questions
- Does repeating the same spreadsheet formula on the same data collect new evidence?
- What is replicability in the National Academies’ specific definition?
- Why does the second airplane round change the simple story told by the first?
- What is the combined B-minus-A difference across the invented rounds?
- Why might two rigorous studies obtain different numeric results?
- What details would another person need before attempting a new airplane experiment?
Compare your answers
1. No; it checks the calculation but does not collect new observations. 2. Consistent findings across studies addressing the same question with their own data, interpreted in light of uncertainty. 3. The apparent winner changes; five observations per design are unstable. 4. +0.02 m. 5. Variation, context, measurement differences, or limits of the original conclusion may matter. 6. Materials, construction, conditions, trial order, outcome definitions, measurement rules, analysis plan, and deviations.
Reflection · The strength to return
A first result can open a door. The second attempt tests whether the door leads where we thought. Science grows stronger not by banning uncertainty, but by making the steps available to be examined again.
Takeaway: Record the method. Check the calculation. Gather new observations. Compare carefully. Report uncertainty. Revise what the evidence supports.
Completion: You have completed Lesson 012 when you can distinguish computational reproduction from independent replication, reproduce the worked averages, and propose one clear improvement to the test procedure.
Sources & further learning
- National Academies (2019) — Reproducibility and Replicability in Science, definitions.
- National Academies — Reproducibility chapter.
- NIST Engineering Statistics Handbook — Experiments and Experimental Design.
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Nova Academy is a free, non-accredited learning resource of the Electric Icarus Project. The airplane measurements and comparison rounds are invented teaching data, not results of a performed study.
