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A1.10 · Draw and justify evidence-based conclusions

Learn to draw and justify evidence-based conclusions through clear examples and targeted practice.

Ontario Grade 10 Science

Scientific Investigation and Careers

Use observations and data to make conclusions that your evidence can support

In Grade 9 science, you learned to observe and record what happens during an investigation. In Grade 10, you also need to explain what those observations support. A conclusion is not simply a guess or a repeat of the results. It is a clear answer based on evidence, with a reason that connects the evidence to the answer. This lesson practises that skill using simple, clearly labelled hypothetical examples.

What you will learn

Tell the difference between an observation, evidence, and a conclusion.
Write a conclusion that answers an investigation question and matches the evidence.
Justify a conclusion by explaining how specific evidence supports it.
Recognize limits in evidence and avoid claims that go beyond it.

From observations to a conclusion

An observation is something you notice or measure. For example, you might observe that one paper towel absorbs more water than another. Evidence is the information from observations that is relevant to a question. A conclusion is your answer to that question, based on the evidence.

A useful Grade 9 bridge is to ask: What did I see or measure? Keep that separate from: What does it suggest? For instance, “the towel held 18 mL” is a result. “This towel absorbed more water than the other towel” is a possible conclusion, if the comparison is supported by the results.

A conclusion should answer the investigation question directly. It should also say what evidence supports the answer. The explanation connecting evidence to the conclusion is the justification. In simple terms: state your answer, point to the relevant evidence, and explain why that evidence supports your answer.

Observation: what you noticed or measured.
Evidence: observations relevant to the question.
Conclusion: the answer supported by the evidence.
Justification: the explanation of how the evidence supports the conclusion.

Make a claim that fits the evidence

Imagine that a class wants to know whether a shaded place is cooler than a sunny place at lunchtime. Temperature is the quantity being compared. A thermometer reading is an observation. A set of readings from both places can provide evidence.

Before drawing a conclusion, check that you are comparing like with like. Were the readings taken at about the same time and in comparable conditions? Was the same type of thermometer used? These questions help you judge whether the evidence is useful for the question. They do not prove that every other factor was identical.

A conclusion must stay within the scope of the evidence. If readings show that one place was cooler on three observation days, you can say it was cooler on those days. The results do not, by themselves, show that it is always cooler there or explain every reason for the difference.

When several observations point in the same direction, they may support a conclusion more strongly than one observation. If results vary, report that variation rather than hiding it. Evidence can support a limited conclusion even when it does not settle every question.

Compare evidence that relates to the same question.
Mention the conditions or limits that matter to the conclusion.
Do not claim more than the observations support.
Describe mixed results honestly.

A simple model for reasoning

You can organize your reasoning with three parts: conclusion, evidence, and connection. First, state the answer. Next, give specific observations or measurements. Finally, explain how those observations support the answer. This is a planning model, not a special scientific equation.

For example: “The shaded location was cooler during the observations. Its recorded temperatures were lower than the sunny location’s on each of the three days. Because the readings were taken at the same time at both locations, they support this comparison for those days.” The final phrase keeps the conclusion within the evidence.

A diagram or table can help you see a pattern before writing. A table lists observations in an orderly way. A diagram can show where observations were made. Neither one replaces the written justification: the reader still needs to know which evidence matters and how it supports the conclusion.

Conclusion: answer the question.
Evidence: give the relevant observation or measurement.
Connection: explain why the evidence supports the answer.
Use careful wording to show how far the conclusion reaches.

Check the evidence and work safely

Evidence is more useful when observations are recorded clearly and the comparison is fair. A fair comparison means that the conditions that matter to the question are kept as similar as practical, while the relevant difference is observed. If an important condition changes, mention it because it may affect how confidently you can compare the results.

Do not invent results to make a conclusion sound stronger. In examples and practice, clearly label made-up values as hypothetical. In a real investigation, record what happened, including unexpected or unclear results.

Follow your teacher’s directions and classroom safety rules when collecting evidence. Use only approved equipment and procedures. Do not try an investigation at home if it involves unknown materials, heat, electricity, sharp tools, or other hazards. A conclusion is only as trustworthy as the evidence gathered, and evidence must be gathered safely.

Record what happened rather than what you expected to happen.
Notice conditions that could affect the comparison.
Label practice data as hypothetical.
Follow classroom instructions and safety rules.

Worked example

Comparing two paper towels

Hypothetical data: A class places equal-sized pieces of two paper towels in the same amount of water for the same length of time. Towel A holds 16 mL after draining, and Towel B holds 11 mL. Write and justify a conclusion about which towel absorbed more water in this test.

Answer the question
The question asks which towel absorbed more water under the test conditions. Keep the conclusion limited to this test rather than claiming the same result for every towel or situation.
Select the evidence
The recorded amounts are 16 mL for Towel A and 11 mL for Towel B. Both pieces were tested using the same stated conditions, so these values are relevant to the comparison.
Connect the evidence
Since 16 mL is greater than 11 mL, the evidence supports the conclusion that Towel A absorbed more water in this test.
$16\,\mathrm{mL} > 11\,\mathrm{mL}$

Answer: Towel A absorbed more water in this test. It held 16 mL, compared with 11 mL for Towel B, and the pieces were tested under the same stated conditions.

Check: The conclusion names the comparison, uses the measurements, and does not claim that Towel A will always absorb more in every situation.

Worked example

Reading a short series of observations

Hypothetical data: A student records the temperature in a shaded and a sunny location at the same time on three days. The shaded readings are 18°C, 19°C, and 18°C. The sunny readings are 21°C, 22°C, and 20°C. Draw a conclusion and justify it without claiming more than the data show.

Look for a pattern
Compare the readings from the same day. Each sunny reading is higher than the shaded reading for that day.
$21 > 18,\quad 22 > 19,\quad 20 > 18$
State a conclusion within the evidence
The repeated comparisons support saying that the sunny location was warmer during these three observations. They do not establish what temperatures will be on other days or at other times.
Give the justification
The readings were taken at the same time at both locations, and the sunny-location value was higher on all three days. That consistent pattern supports the limited conclusion.

Answer: The sunny location was warmer than the shaded location during the three observations. Its recorded temperature was higher on each day when the locations were compared at the same time.

Check: The evidence supports a comparison for the observed days. It does not identify every cause of the temperature difference.

Worked example

When results do not all agree

Hypothetical data: Two groups compare how far a toy car rolls on two surfaces. Group 1 records 84 cm on Surface X and 70 cm on Surface Y. Group 2 records 73 cm on Surface X and 76 cm on Surface Y. What conclusion is justified?

Report both comparisons
Group 1 measured a greater distance on Surface X. Group 2 measured a slightly greater distance on Surface Y. The results do not show the same pattern in both groups.
$84\,\mathrm{cm} > 70\,\mathrm{cm},\quad 76\,\mathrm{cm} > 73\,\mathrm{cm}$
Avoid hiding the difference
Using only Group 1’s result would leave out evidence that does not match. A justified conclusion must account for both groups’ observations.
Draw a careful conclusion
These results are mixed, so they do not clearly show which surface lets the car roll farther. More carefully collected evidence could help clarify the comparison. The current data do not justify choosing one surface as the clear winner.

Answer: The results are mixed and do not clearly show that either surface lets the car roll farther. One group measured a greater distance on Surface X, while the other measured a greater distance on Surface Y.

Check: The conclusion acknowledges all the evidence and does not force a clear answer from results that disagree.

Common mistakes and how to avoid them

Repeating a measurement without answering the investigation question.

Correction: State what the evidence suggests in direct answer to the question, then include the measurement that supports it.

Making a claim that goes beyond the observations, such as saying a location is always warmer based on three days of readings.

Correction: Limit the conclusion to the conditions and observations that were actually recorded.

Leaving out evidence that does not fit the preferred answer.

Correction: Include relevant results that agree and disagree. If the evidence is mixed, say so.

Treating a conclusion as proof of a cause when the investigation only recorded a comparison.

Correction: Describe what the evidence shows. Do not name a cause unless the evidence supports that claim.

Lesson summary

An observation is something noticed or measured; evidence is information relevant to the question.
A conclusion answers the question, and a justification connects the answer to specific evidence.
Use all relevant results, including results that disagree.
Keep the conclusion within the conditions and limits of the evidence.
Record evidence honestly and follow safety directions.

Check your understanding

Question 1

A student compares two plants for one week. Plant A grows 2 cm and Plant B grows 3 cm. Which conclusion is best supported?

Plant B grew more than Plant A during this week.
Plant B will always grow faster than Plant A.
Plant A cannot grow in the conditions used.
The evidence proves exactly why Plant B grew more.

Show answer and explanation

Plant B grew more than Plant A during this week.

The recorded growth supports a comparison for this week. It does not establish what will always happen or explain the cause.

Question 2

Which part of a conclusion explains why the evidence supports the answer?

The investigation question
The justification
The equipment list
A prediction made before the investigation

Show answer and explanation

The justification

The justification connects the evidence to the conclusion.

Question 3

Two groups get results that point in opposite directions. What should you do?

Report only the group whose results support your first idea.
Change one result so both groups agree.
Describe the mixed evidence and make a limited conclusion.
Claim that neither group collected any evidence.

Show answer and explanation

Describe the mixed evidence and make a limited conclusion.

A sound conclusion accounts for relevant results, including disagreement, and avoids claiming more than the data support.

Key terms

Observation: Something noticed or measured during an investigation.
Evidence: Observations or measurements that are relevant to answering a question.
Conclusion: An answer to an investigation question that is based on evidence.
Justification: An explanation of how specific evidence supports a conclusion.
Hypothetical data: Made-up values used for practice, not results measured in a real investigation.

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About this lesson and its review

Published by DoAssignment. This reviewed lesson follows Ontario Grade 10 Science (SNC2D), expectation A1.10. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

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