This is my 300th post! *confetti*
By student experiment, I'm assuming you mean you conduct a practical investigation and are required to do a write-up on it.
1. Specificity is key
This applies to the write-up component. Don't say 'x error impacted the experiment and could cause the results to change' - instead explain how the error could have impacted on the experiment and how the results could change (increase? decrease? why?). Be very specific in the methodology and apparatus sections too. Someone reading your experiment should be able to replicate it exactly as you did it, so write your instructions and materials with this in mind.
2. Use correct language
Write the method in past tense if possible, and use correct scientific terminology. Don't say the hypothesis is proved/disproved, say it is supported/negated/rejected. This is a major point many students seem to slip up on. Also, don't say 'x error could be eliminated through the use of y next time' or 'x error was eliminated due to y'. You can never completely eliminate any error with confidence, so the correct word here would be 'minimised' or 'controlled'.
3. Hypothesis
Ensure your hypothesis addresses all aspects of being a hypothesis. It must be a testable prediction. For psychology, your hypothesis will 99% of the time follow the following structure: population - IV - DV - the direction of prediction word - IV. For biology, the if-then structure seems to be preferred. I'm not too sure about physics, however, it shouldn't be too different. Don't write your hypothesis incorrectly - you are losing easy marks. Take time to carefully word it out well - it will pay off in the end.
4. Conduction of experiment
It is okay to make errors. In fact, do make errors! This gives you more to talk about in the discussion when discussing limitations, errors and improvements. If you conduct a "perfect" experiment, you will have very little to discuss when you do your write up. Obviously don't completely stuff up your results, as you still want to be able to analyse results and be able to conclude whether the hypothesis was supported or not. But don't be too worried about mistakes in your experiment.
Other tips:
- Ensure handwriting is legible, if they can't read it they won't attempt to 'figure out' what it says and you will lose marks - a friend of mine in 1/2 psych lost a mark due to one word being illegible and so the teacher couldn't make out what he was saying in that sentence. This is overlooked but important.
- For biology, a systematic error present in nearly all experiments is contamination error - this is something to talk about.
- For all sciences, you can talk about how the experiment can be repeated/multiple trials should have been conducted
- For psych and bio, always mention how due to the sample size being small, the sample is unrepresentative of the population, thus compromising validity. Usually your sample size will be small so you will be able to talk about this.
- Ensure you know the meaning of accuracy, precision, reliability and validity - these are very important to know and don't get confused by what they each mean
- Be concise and clear - don't make anything vague/hard to understand
- All scientific diagrams should be in 2D, they should not be in 3D and should not be coloured in
- Revise research methods/scientific method content
- Know the theory behind your experiment otherwise you won't be able to write the discussion properly