It is diffcult to give very clear guidance to help you with your conclusion as it partly depends on what the marks are going to be awarded for. To help you with this, it would be useful if you got a copy of the mark scheme and coursework guidance that the exam board may produces. Most exam boards now have this information on their wen site, so if you know which one it is, you should be able to get hold of a copy quite easily. It may be part of the 'specification' (a document that specifies what the course is about), or may be some additional guidance. Use any guidance that you teachers give you too, looking at what they say marks are awarded for.

In general, the conclusion is likely to include a summary of your research - a recap of the main points that your research was about - what the key questions to research, main points about the methods of data collection and analysis, together with a summary of the main findings and the main reasons for these. None of this is new information, but shjould follow from the rest of your report. You will also need to include an evaluation - this would include what improvements could be made to gain more reliable results (I like to think of this in the following way - if someone was to pay you to carry out this research to a high standard, what would you do differently & why), and also put in what further research questions follow on from your findings.

Hope this pointers are of some help.