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CAIE A-Level Biology AS P3.8 Conclusions Errors Improvements and Extensions Questions

Use complete AS questions to distinguish a fixed systematic bias from random variation and decide whether experimental results support a conclusion while retaining…

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • Classify an error as systematic when the same endpoint offset is applied consistently, and explain why repeats reduce random variation but do not remove that fixed bias.
  • Judge whether results support a treatment or hypothesis by presenting evidence on both sides and qualifying the conclusion with limitations such as sample size or incomplete information.

CAIE A-Level Biology AS P3.8 Conclusions Errors Improvements and Extensions Questions question 1

[Maximum number: 1]

A student carried out the Benedict's test on four different concentrations of glucose solution and then recorded the time taken for the first appearance of a colour change (the end-point).

The student found it difficult to identify the first appearance of a colour change and consistently timed each solution for two seconds after the colour change first appeared. This introduced a source of error into the experiment.

Which statements about this error are correct?
1 The effect of the error will be reduced if the student performs three repeats at each concentration of glucose.

2 The error will prevent the student from identifying which solution has the highest concentration of glucose.

3 The error is systematic as the student consistently timed each solution for two seconds after the end-point.

A

1 and 2

B

1 and 3

C

2 and 3

D

3 only

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