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Analysing and Evaluating Practical Results

Anomalies, limitations and refining a procedure

  • 3 things to know
  • Components 01, 02 and 03

Overview

Recall questions on identifying and dealing with anomalous results and their causes, limitations of procedures such as potometers and counting bubbles, and refinements including gas syringes, repeats, colorimeters and data loggers, and consistent rest periods in pulse rate studies.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Evaluation

What should be done on noticing an anomalous reading, when may an anomaly be left out of a mean, and why take at least three repeats?

Key term

What should a student do on noticing an anomalous reading while the experiment is still running?

Key term

Under what circumstances may an anomalous value be left out when a mean is calculated?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is an anomalous result?

    Model answer

    It is a measurement that lies well outside the pattern shown by the rest of the results.

  2. 2

    How is an anomaly identified within a set of repeats taken at one value of the independent variable?

    Model answer

    It is the repeat that differs markedly from the others, and on a graph it appears as a point lying far from the line of best fit.

  3. 3

    What should a student do on noticing an anomalous reading while the experiment is still running?

    Model answer

    Repeat that measurement to check it, and look for a cause such as a procedural mistake or a fault in the apparatus.

  4. 4

    Under what circumstances may an anomalous value be left out when a mean is calculated?

    Model answer

    Only when there is good reason to believe it arose from an error in the procedure, and the omission must be stated.

  5. 5

    Give two possible causes of an anomalous result in an enzyme investigation.

    Model answer

    The water bath may not have reached the set temperature before the run began, or the volume of enzyme may have been measured out inaccurately.

  6. 6

    What is meant by a limitation of an experimental procedure?

    Model answer

    It is a feature of the method that restricts how accurate, precise or valid the results can be, even when the method is followed correctly.

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