Assess challenges to inferences
Challenge the exact step from evidence to claim and judge whether a response actually repairs it.
Section Papers 2 and 4 · Evidence, argument and applied reasoning
Original StudyForA scenarios and formative model answers; no Cambridge marks, predicted grades or certified mastery. Alternative reasoned answers may be valid. Full-length unseen papers, a wider mixed-problem bank and calibrated specialist teacher marking remain outstanding.
Before you begin
- Read an English passage closely
- Distinguish a statement from its supporting reason
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Before evaluating support, what should you identify?
What you will learn
- Suggest a relevant challenge to an inference
- Assess the force and limits of a reply
Target the inferential bridge
An effective challenge identifies what the evidence fails to establish: representativeness, causation, sufficiency or the scope of a conclusion. Attacking a person’s character is not a response to the logical step. A reply must address the identified gap, rather than offer unrelated positive information.
An app-only survey is used to claim all residents support online booking. A challenge points to exclusion of non-app users. ‘We received many responses’ does not answer that concern; it addresses size rather than the selection mechanism.
A challenge can weaken without reversing
A challenge can make an inference less secure without establishing its opposite. A reply can partially repair a weakness without settling every issue. Assess exactly which uncertainty remains after considering the response.
When proposing a challenge, connect it to the given source and conclusion. General scepticism that ‘all surveys are flawed’ ignores the actual design and may be unsupported. A counterexample is decisive against an unqualified universal claim, but not necessarily against a cautious average claim.
Sources for this lesson
Pause and explain
Which reply addresses app-only exclusion?
Worked example
Does doubling app-only responses answer the exclusion challenge?
Show the worked solution
- The concern is missing non-app users.
- The same app-only recruitment remains.
- More of the same respondents does not repair that gap.
Answer No. The larger sample may improve precision within app respondents but does not address exclusion of non-app users. The all-resident conclusion remains insufficiently supported.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Guided: Form a precise challenge to the all-resident booking inference.
Give me a hint
Name the missing group and why it matters.
Compare my reasoning
- Recruitment occurs only on the app.
- Non-app residents may have different access needs.
- Their preferences are not established.
The sample excludes residents unable or unwilling to use the app, whose booking preferences may differ. Therefore app responses cannot establish support across all residents without additional representative evidence.
Look for these in your work
- Identifies the mechanism
- Links it to preferences
- Targets the conclusion
Independent: A claim says every student can reach school by bus. One student lives beyond the bus network. What does this evidence challenge?
Give me a hint
Focus on the universal quantifier.
Compare my reasoning
- The claim covers every student.
- The student is within the population but lacks a route.
- One valid exception defeats the universal claim.
The case challenges the unqualified ‘every student’ claim. It does not show buses are useless for most students; it shows an exception that requires a narrower statement or an alternative arrangement.
Look for these in your work
- Uses the universal scope
- Explains the counterexample
- Avoids overgeneralising the challenge
Application: After the app survey challenge, a random address-based survey with accessible paper responses finds similar support. Assess the reply while noting remaining checks.
Give me a hint
Identify which gap has been addressed.
Compare my reasoning
- Recruitment now reaches beyond app users.
- The similar result provides additional support.
- Check coverage, non-response and question wording.
The reply directly addresses the exclusion concern and strengthens the all-resident inference if the address frame and response process are representative. Similar findings alone do not remove every issue; non-response and wording still need assessment.
Look for these in your work
- Recognises the targeted repair
- Explains its force
- States remaining limits
Common mistakes
- Answering a selection criticism with sample size
- Making an unrelated personal attack
- Assuming any challenge proves the opposite
What can you explain now?
Which reply addresses app-only exclusion?
Compare with the explanation
Recruiting relevant offline users too
The reply must change the selection mechanism that caused the criticism.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Which reply addresses app-only exclusion?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.