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What factors must be considered when assessing the use of evidence?

• Precise relevance to reason
• Sufficiency to support claim
• Selective use of evidence
• Averages -> Representative of whole group?
• Alternative explanations


In what way must evidence be relevant to the reason it is supporting?

• Timescale
• Group of people
• Geographic area


Assess the use of evidence:

“In 2005, Detroit police used undercover surveillance and informants to fight organised criminals, and reduced crime by 72%. This shows that the British government doesn’t need to invest more money in police weaponry - guns are not the only way to tackle violent criminals.”

1) Evidence is about Detroit, but it’s used to support a claim about British police -> Not precisely relevant -> British police might have different skills, etc.
2) Evidence is about organised criminals, but it’s used to support a claim about violent criminals -> Not precisely relevant -> Techniques for dealing with organised criminals may not work for violent criminals


What makes evidence relevant?

It has to be about exactly the same thing as the reason.


How does relevance of evidence affect the strength with which the evidence is used?

• Not precisely relevant -> Weakness
• Relevant in any way -> Strenghtens


Why must evidence be sufficient to support a claim?

A reason has to be fully supported by evidence in order to be strong.


Assess this use of evidence:

“We Know Cyprus will be a great place for a holiday - it gets 326 days of sun a year.”

• Insufficient evidence -> Weak
• Lots of sun may be relevant to having a great holiday, but it’s not enough on its own
• We need evidence about other factors


What is selective use of evidence?

When certain information is withheld in supporting a reason.


Assess the use of evidence:

“Many smokers use cigarettes to relieve stress - and with good reason. A scientific analysis of tobacco found that it causes the brain to release hormones that make you feel more relaxed. Stress is bad for your health, so this proves that cigarettes are good for your health.”

• Selective use of evidence
• Evidence about the dangers of smoking, such as cancer, are withheld
• This would prove that smoking is not completely good for your health


Why is selective use of evidence / insufficient evidence a weakness?

• The reason won’t be fully supported
• Strong use of evidence requires all the information needed for us to accept that the reason’s true


What’s the difference between insufficient evidence and selective use of evidence?

• Insufficient -> The evidence provided is not enough to fully support the reason.
• Selective use of evidence -> There is other evidence that could prove the opposite and weaken the reason


How may averages not be representative of a whole group?

• There are different types of average -> Can be manipulated
• Also, averages only give a rough idea of a whole group -> May not be strong enough to offer support for a reason


Assess the use of evidence:

“Kathryn is an excellent instructor. The average time it takes her to teach someone to drive is 67 hours, so there’s no need to budget for more than 80 hours’ worth of lessons.”

• Average is not representative of the whole group
• For some people it may take far longer than 67 hours to drive, so they may need to budget for more than 80 hours


How do you evaluate evidence from a graph or table?

• Just like with normal evidence
• Check that it is relevant, sufficient and representative


Remember to revise assessing evidence from a graph or table.

Pg 43 of revision guide


What is the effect of alternative interpretations of evidence?

If you can offer an alternative explanation for a piece of evidence, it weakens the author’s claim


Assess the use of evidence:

“Newly qualified drivers aged 17-20 are twice as likely to have a crash as more experienced drivers. This shows that the practical driving test is too easy.”

• There are alternative explanations for this evidence
• e.g. Young drivers may be more immature and likely to take risks
• This weakens the use of evidence


What two types of question might you get about evidence?

1) Multiple-choice deciding which piece of evidence most strengthens or weakens an argument
2) Explain one strength or weakness in the use of evidence


When answering questions about strengths or weaknesses in the use of evidence, what is it important to do?

• Don’t just state the strength or weakness.
• Explain how the use of evidence connects to the reasoning.

“The evidence is weak because the survey only covers office workers.”
“The evidence is weak because it only covers office workers and cannot be applied more generally to all work environments such as hospitals or schools, so it doesn’t support the claim that tea needs to be banned in all workplaces.”


Can examples on their own be used to support conclusions?

No, they can make reasons more convincing, but they can’t support the conclusion without the reason.


Why are examples used?

To make reasons more convincing.


What must you do when asked to assess the use of examples in an argument?

• Check to see if the example supports a reason -> On its own, the example is weak
• Check the example is relevant -> Same situation as in the reason + typical of the group


Evaluate the use of examples:

“Our bulldog is wonderful with children - he lets them pull his tail and play with him and is very patient with them. Clearly bulldogs are the perfect family dog.”

• Only example supports the conclusion, no reasons -> Weak
• The example is only about one dog, so there’s not enough reasons to accept a general conclusion about all bulldogs


What things make an example relevant?

• Precisely the same situation as the reason -> Timescale, Area, People
• Typical of the group being discussed -> i.e. Not a exception


Evaluate the use of examples:

“Exercising isn’t a good way to lose weight. When Matt Hegarty was training for a marathon, he was exercising for at least 2 hours a day every day - and he put on weight.”

• Example isn’t relevant.
• The reason is about people wanting to lose weight, but Matt was exercising for a marathon, not to lose weight.


Evaluate the use of examples:

“Horror films often have serious effects on people’s mental health. Last year, a young man attacked and murdered an innocent passer-by just hours after watching Screwdriver II at the cinema.”

• Example is an exception -> Not relevant.
• One man’s extreme actions aren’t representative of the large group of people who watch horror films.


Is it bad is an example illustrates an exception?

Usually yes. But not if they support a claim that states that *sometimes* something can happen.


Evaluate the use of evidence:

“Doing exercise isn’t always good for you. Runners can damage their joints because it’s a high impact sport, and snow-boarders frequently break bones. So always check with your doctor before starting a new exercise regime.”

• Example is relevant, even though it illustrates an exception.
• Because it supports the claim that *sometimes* exercise can be bad for you.


When assessing the use of general principles, what factors must you consider?

• Relevance
• Principle that applies in many situations
• Relative strength of opposing principles


In what way must a general principle be relevant?

The principle must be proved to be relevant to the conclusion, usually by other reasons that show it to be true in this situation.