Claim, Evidence, Reasoning, and Rebuttal

How to write a scientific argument

Thomas Huxley quote

Claim Most labs originate with a guiding question. Your claim is the concluding statement that answers your original question. ● The claim is one sentence in length.

● It must be accurate, specific, and

completely answer the question.

Evidence The evidence is all of the scientific data that supports your claim. ● Evidence must be sufficient and relevant to

your claim. Not all data is considered evidence! ● Most evidence is specific data from the lab.

This can come from your own group or another group in the class.

Evidence The evidence is all of the scientific data that supports your claim. ● It can also come from other sources such as:

computer simulations, websites, textbook, class notes, personal experience, observations, etc.

● It is important to have numerous pieces of

evidence in order to prove your claim!

Reasoning

Reasoning is the explanation that connects your claim to the evidence that supports it. ● It shows why the data you chose counts as evidence.

● It is the link between the evidence and the claim.

● This explanation acts as a “conclusion” of your experiment.

Reasoning Reasoning is the explanation that connects your claim to the evidence that supports it. ● It shows a detailed understanding of the

scientific principles involved and uses correct scientific vocabulary. ● The reasoning should be several sentences in

length. (Usually a sentence to explain each piece of evidence)

Rebuttal

●  Describes alternate explanations for the driving question. ● Provides counter evidence and reasoning for why the alternate explanation is not appropriate. ● Think about: if someone were to disagree with you, what evidence would they provide and how would you try and convince them that they are incorrect?

● Data Collected:

Weight Lifted Patrick John

Starting Amount 110 lbs 80 lbs

After 1 week 150 lbs 100 lbs

After 2 weeks 215 lbs 180 lbs

Question: Does the new muscle lotion really double a person’s muscle power?

● Claim: The new muscle lotion does not double a person’s muscle power.

● Evidence: Patrick received the new muscle cream as part of his muscle-building workout and the amount of weight that he could lift over the two week period increased from 110 lbs to 215 lbs.

EVIDENCE

● Reasoning: If Patrick’s muscle power had doubled, he should have been able to lift at least 220 lbs after the two weeks, so he was 5 lbs short of meeting the requirement.

REASONING

● Rebuttal: Some people might think that the muscle lotion does increase a person’s muscle power more than the regular lotion because Patrick was able to lift more weight (215 lbs) than John (180 lbs) at the end of the two weeks. However, this is incorrect because the people need to be compared to their own starting amount, which shows that John had a larger percent increase of 225% compared to Patrick’s increase of 195%.

REBUTTAL

Some people may claim that the muscle lotion does work because Patrick was able to increase his muscle power over the two weeks. However, John, who didn’t have the muscle lotion (control group) also saw an increase in strength from 80lbs to 180lbs so we can conclude that the strength increase came from the weight lifting program, not from the lotion.

REBUTTAL #2

Claim: Clearly state how Mr. Xavier died. If you think he was murdered don't just say "He was murdered." You would need to state the cause of death and who murdered him. You need to be specific and concise. Evidence: List all of the related observations and test results that support your claim. Reasoning: Explain why your evidence proves your claim to be true. (Pretend you are a lawyer arguing your case). Rebuttal: Suggest another cause for Mr. Xavier’s death and why it is not possible based on the evidence.

What was the cause of Mr. Xavier’s death?

Claim: Jake Drake murdered Mr. Xavier by causing him to overdose on heart medication.

What was the cause of Mr. Xavier’s death?

● The autopsy showed the cause of death was overdose on heart medicine. ● Jake Drake’s fingerprints were found on the

wine bottle and the heart medicine bottle. ● Robert Drake said his brother had never been

in the house. ● The prescription bottle was empty and it did

not run out for another month.

Evidence:

●  The autopsy and empty medicine bottle prove that Mr. Xavier died of an overdose, which was not accidental or the medicine bottle wouldn’t have been empty.

●  There is no reason for Jake Drake to be inside of the house so his fingerprints should not have been found on the bottle and wine.

●  His motive was that Mr. Xavier had treated his brother unkindly.

Reasoning:

An opposing claim may be that Mr. Xavier was killed by an intruder that broke the window in the dining room and entered the house and killed him with the knife. This is not correct because the autopsy showed that he died from an overdose of his heart medication. Alternative explanations for the other evidence is that the window was broken in the storm and the red stain under Mr. Xavier’s body was red wine, not blood. The cuts were caused by him falling onto the broken wine glass or the window. The knife did not have blood on it but instead juices from his rare steak.

Rebuttal:

Was Robert Drake in on it?

● He either let Jake into the house and lied to the police or he didn’t know Jake was ever in the house. He could be charged as an accomplice but there doesn’t seem to be enough evidence one way or the other.

Question: Does mass affect how quickly an object falls?

Claim, Evidence, Reasoning, Rebuttal

Data that was collected:

Trial 1 Trial 2 Trial 3 Trial 4 Trial 5

Mass of block

20 g

30 g

44 g

123 g

142 g

Time it took to

fall from 3 meters

1.62 sec

1.75 sec

1.50 sec

1.80 sec

1.71 sec

● Claim: Mass does not affect how quickly an object falls.

EXAMPLE: Question: Does mass affect how quickly an object falls?

EXAMPLE: Question: Does mass affect how quickly an object falls? Evidence: The blocks had different masses

of 20g, 30g, 44g, 123g, and 142g. The time for all five blocks to fall was about the same, which was between 1.50 seconds and 1.80 seconds. There is also no pattern to the data. For example the 20 g block fell slower (1.62 sec) than the 44g block (1.50 sec) and the 123 g block fell slower (1.80 sec) compared to 30 g block (1.75 sec).

EXAMPLE: Question: Does mass affect how quickly an object falls? ● Reasoning: Gravity affects all objects

the same regardless of their mass. As long as the objects are massive enough to push through the air resistance that Earth has, they will all fall at the same rate.

EXAMPLE: Question: Does mass affect how quickly an object falls? ● Rebuttal: People may argue that mass does

affect falling speed because the data showed differences up to 0.3 seconds. However, the average human reaction time is 0.25 seconds, so it can be explained that the 0.3 seconds of differences is due to human error when using the stop watch.

REBUTTAL VERSION #2

● People may argue that mass does affect falling speed because a tennis ball falls faster than a piece of paper because it is more massive. However there are other differences between those two objects that do affect their speed (on Earth), such as their shapes. A piece of paper falls more slowly than a tennis ball because it has more surface area and catches more air as it falls, which slows it down.