Monday, November 16, 2009

[Physics SPM] Exam Pointers IV

Source: Maths & Science Guide

State the factors that influence the accuracy of a measurement. [ 4 marks ]

Frequent Mistakes
Student Answers:
Accuracy is evaluated based on how close a quantity's measured value is to its actual value. Accuracy is influenced by the level of error present in the measurement. The presence of error will cause a measured value to deviate from its actual value, thus reducing the accuracy level of measurement. The errors that normally reduce the accuracy of a measurement are parallax error and zero error.

Identify the command word "state" and the objective of the question, which focuses on "the factors that influence accuracy". Since the allocation of marks is four, the answer should consist of four main points. The student's lengthy explanation about errors and how they reduce the accuracy of a measurement is not required. It shows that the student does not understand the objective of the question clearly and accurately. Though the answer is full of factual information, it is low quality as it fails to meet the objective of the question.

Correct Answer
Any four of the following:
  • The selection of the techniques of measurement.
  • Precision of a device.
  • Sensitivity of a device.
  • The selection of a suitable device based on the size of measurement.
  • The presence of error in a device, or due to the experimenter, during a measurement.

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