Mark Guide: Evaluating

E.4

E.4a

comment on the quality of the evidence

The accuracy of your results is determined by the smallest change in the variables that you could measure. Look at all your results and state how accurately you measured them. The accuracy normally depends upon the type of equipment you used, and how easy it was to take the measurements. Some things are difficult to measure accurately when they are changing quickly. The accuracy may be different over the range of results taken. Explain all this in as much detail as possible. If you have done this then explain how the accuracy of each measurement could be improved.

identify any anomalies

• human error
  One or two results may be wrong because you misread them or wrote them down incorrectly. These should be fairly easy to spot. Identify any results which fall into this category. All these results should, of course, have been removed before an average is calculated or a graph is drawn. If you have left them on your graph then make sure you circle them and label them as wrong.
• equipment error
  The equipment may have produced a few faulty readings. Again, these should be removed before results are analysed. Alternatively the equipment may have been reading consistently high or low. If you know what the error is then results can be corrected to allow for it.
• scientific anomaly
  If you are lucky you may get a true scientific anomaly. This is something which you discover from your results but you weren't expecting from your prediction. This gives you lots to discuss in your analysis and is after all what makes science fun. Wouldn't the world be a dull place if everything was perfectly regular?
• Inaccurate results are not anomalous
  With a low accuracy you can't expect a smooth pattern with all the points close to your line of best fit. This does not make your results anomalous just inaccurate. Note that it does not matter that you have a low accuracy if this is the best that can be achieved with a difficult experiment.
• No anomalous results
  State you haven't got any, and how you know there aren't any.

E.4b

comment on the suitability of the procedure

Go through each bit of the procedure and explain how and why it worked well or didn't work so well.

suggest changes to improve the reliability of the evidence

Explain how the procedure could be improved to make it more accurate or more reliable.

• More repeats needed?
  • Explain what needs repeating,
  • why it needs repeating,
  • and how many times you need to repeat.
• More in between results needed?
  • Explain what extra values you need to measure,
  • and why you need to measure them.
• Bigger range of results needed?
  • Explain what additional range you need to measure,
  • and why you need a bigger range.
• More equipment?
  • Explain what extra equipment you need,
  • explain why you need it,
  • explain how you would use it.