Skill E-Evaluating Evidence

To get a mark of 2:

• You need to compare the outcome with your original intention. (Did your practical work help you to get information to test your original idea?)
• You need to comment on whether you think your procedure was fair.

To go on and get a mark of 4:

• You need to say whether or not your results were sufficiently accurate for you to draw a conclusion. (Were you able to use them to pick out a pattern? What errors might there have been in your measurements?)
• You need to pick out any anomalous results that do not fit the overall pattern of your results. (If there aren’t any, then say so!)
• You should discuss whether the procedure was suitable for what you were trying to do? You should think about the reliability of your results. (If you have repeated your sets of readings, are they sufficiently close to enable you to take averages? If not, did you have any difficulties in making judgements or taking observations?)
• You should try to suggest what simple changes you might make to improve the reliability of the procedure.

To improve on this and get a mark of 6?

• You need to make comments about the reliability of the procedure. (Your criticism of the apparatus and techniques should be detailed and specific, eg. ‘The digital meter reading changed continually over a small range, suggesting problems with the power source’.)
• You should suggest an explanation for any anomalous results. (eg. ‘The reaction may have taken longer than it should have for that temperature because the reaction mixture cooled from its starting temperature as the reaction was happening’.)
• You need to make an attempt to judge how safe your conclusion is, based on the range and quality of the evidence you have used to justify it. (eg. ‘My conclusion is likely to be correct since all the results supported it, though I only had time to vary the concentration over a limited range of values, so I am not sure how true it is outside that range’.)
• You need to propose improvements or further work to provide additional evidence or to extend your enquiry. (Try to be specific and realistic. Improvements should add to the investigation of the original prediction – there is no point in suggesting the investigation of another variable, since this would be a different investigation. As an example, if the original prediction concerned the effect of concentration on the rate of a reaction, it is not relevant to suggest the enquiry could be extended to look at the effect of temperature. It would be better to suggest another way to investigate the effect of concentration.)