Lab Report Evaluation guidelines....

[hel]

I really need to get a complete on evaluation, but my teacher says I have to redo it...

are there any tips/guidelines how to write up evaluation?

I've used the marking scheme guidelines, but I need some more tips

[Greentea]

Well, yes there are probably, but the guidelines would be very general, since it will depend entirely on the lab itself. I often use this guide, to write up the evaluation. What also might be, that you actually made mistakes in evaluating, meaning that u followed the guidelines,but ur evaluation was wrong.

[Keel]

I really need to get a complete on evaluation, but my teacher says I have to redo it...

are there any tips/guidelines how to write up evaluation?

I've used the marking scheme guidelines, but I need some more tips

I don’t take physics, just chemistry, but I'll assume that the purpose of the CE (conclusion and evaluation) is the same in both subjects. If you're only interested in the evaluation bit I'll ignore the conclusion aspect.

What you should be provided with is a literature value for the experiment you have done. This is important because it is an indication of how accurate your experiment was. So the first step is to find out how 'off' your obtained value (the answer reached in your DCP) in comparison with the literature value. This can be done by calculating the % difference:

[(obtained value - lit. value) / (lit. value)] x 100% = % difference in answers

This % now gives an indication of how inaccurate your experiment was. There are now two types of errors or areas of improvement you should consider. The first is improving the equipment that you used in your experiment, thus reducing the effect of random uncertainties; and the second is improving the way the experiment was conducted, or fixing the systematic errors.

You should now comment on which type of error contributed most to this inaccuracy. In your DCP, you should have calculated the total % error due to random uncertainties (ie the +/- ...% at the end of your answer). You can use this to find out what % was caused by systematic errors.

(% diff in answers)% - (total error caused by random uncertainties)% = (total error caused by systematic errors)%

You now have an indication of which error is more responsible for your inaccuracy. It is usually the systematic error. You then state which error is more responsible. You should then proceed to state improvements for both types.

For the first type, random uncertainties, go through all the equipment you've used in the experiment, state the % error they caused and propose an improvement. e.g. 50 cm3 measuring cylinder; +/- 0.5 cm3 caused a 10% error; propose to use a 50 cm3 pipette.

The second type usually requires some imagination and a general understanding of the limitations to the experiment. What systematic errors could have caused inaccuracy? State this systematic error, state which direction it moved your result, state whether it's a minor or major error, and state an improvement. e.g. Heat Loss; Caused obtained value to be higher than actual value; Major error; Use insulative container.

I hope this helps, remember this all comes from a chemist and you should adapt it for your purposes.

P.S. The chemistry forum has some good IA help resources if you need further help:

Also you should check the mark scheme: http://ibchem.com/IB/ibe/IA-2009.htm