Your graph may be neat, colourful and pretty, but is it any use?
These are not used very often.
If you draw a bar chart
when you should have drawn a line graph
you will NOT get 6 marks
Bar charts are usually only used for categoric variables. Examples might be species of wild flower, different colours, or different types of material.
In general follow these rules;
To get 6 marks your line of best fit must be good enough that the person marking it (i.e. your teacher) could not significantly improve it. A line of best fit shows the pattern you (think) you would get if you were to remove all the random measurement errors from your experiment. This is not the same as a theoretical line you might calculate from an equation. Real life is often much more complex than a simple theory because many factors can not be perfectly controlled or taken into account.
Remember, a line of best fit can be curved as well as straight. If you can't draw a neat, thin curved line by hand, then you can buy a special flexi-curve ruler to help!
Taking an average of your results does not count as a numerical method. Measuring slopes of graphs (e.g. to work out rates), or working out the equation of a line would count. Any sort of numerical work where evidence is processed so that it can be used for a conclusion counts. e.g. calculating the energy per gram of fuel, or the rate at which gas is produced in centimetres cubed per second.
Your conclusion must agree with your evidence. Your conclusion is a concise written summary of what your graph or calculations show.
Higher level knowledge is not needed for 6 marks.
You must compare your conclusion with your prediction. Some parts may match well,
other parts may not. If not, can you think of possible (scientific) reasons why.