Why you shouldn’t rush when writing a lab report Conclusion

A typical student as they start to write the Conclusion section of their lab report: “AAAGHGHGHGGHGHGH!!! I’m bored now!!!” 

Even if you have started your lab report with all the best intentions, you conducted thorough and detailed research, wrote the other sections clearly and succinctly, and spent a long time transforming your data into amazingly presented graphs, by the time you are ready to write your Conclusion, it is hard to maintain momentum.

If this is the case, take a well-deserved break, and hit this section with some clear ABEL-delivered tips and enough energy to tick all the boxes your teacher and the mark scheme require. The Conclusion can be a tough section to write, and that is why many assessment rubrics and science departments focus on this section to decide who gets the top marks. In conjunction with the Evaluation, this section shows which scientists can use the information they have generated, transformed, analysed and evaluated to write some of their own thoughts, not just deliver information like you have to do in the Background Information section. 

The Conclusion requires you to look at the experiment as a whole in order to answer the Research Question, describe what happened in your experiment, and importantly, explain why that happened—based on the science contained in your Background Information.

What needs to go into a great Conclusion?

As ABEL has recommended throughout this series of articles on How to Write a Great Lab Report, to get the top marks the best thing you can do is use the mark scheme or marking rubric for the task. 

If your school/teacher/science department doesn't provide these, you can approach your teacher directly. In plenty of time before any deadline, ask them what they are looking for in a good lab report, or even better if you both have the time, what they are looking for in each section. ABEL will give you a good idea of what is generally needed in each section, and you can look at these example markschemes and rubrics. 

In general, a great Conclusion:

• Addresses the Hypothesis

• Discusses the results in relation to the Research Question

• Describes the trends in the results

• Provides specific examples of the results

• Explains the trends in the results using science that was presented in the Background Information

• Discusses the validity of the results 

• Describes the impact of erroneous results/measurement errors on the results.

• Discusses the reliability, repeatability, and suitability of the method in relation to the Research Question

• Outlines possible work for the future.

As you can see in the list, these parts need a certain degree of ‘higher-level thinking’ and understanding of the scientific method to write them. Also, this is a lot to fit into a typical Conclusion section, especially depending on what year you are in, but knowing what is eventually required from all scientists will help you focus on the most important parts depending on your experiment/teacher/mark scheme. 

As this is what is required in a great lab report, possibly at the end of your academic year/stage, your teacher may focus on certain aspects of the Conclusion throughout the year. So don’t be afraid to ask what they are looking for!

Always check you have included the units!

When writing a number in a sentence, check you have included the relent units. These are usually written with a space in between them and the number, for example:

 The average was 24 m. 

Exceptions to this rule are degrees and degrees celsius, for example:

Subjects ran up a 20º slope and their body temperature increased by 2.5ºC on average. 

In your lab reports, write out the numbers 1 to 10, except when they are used for units of measurement (mass, time, length, etc.). 

For numbers over 10 use numerals, except when starting a sentence, when all numbers should be written out as a sentence should never start with a number. For example: 

Nineteen woodlice preferred damp conditions, compared to 22 which preferred dry conditions. There were five woodlice that moved over 5 cm in 8 minutes.

When you explain a finding, try to think of each statement as a link in a chain, and you must clearly state what each link is. This can be very briefly, but you can’t jump ahead to other links, you must move step-by-step, explaining as you go. 

For instance, the explanation of why the IV ‘amount of sunlight’ affects the DV ‘height of a plant’ in a positive way (more sunlight → taller plants) could be summarised as:

As the amount of sunlight increases there is more energy available for photosynthesis, the chloroplasts in the plant’s leaves capture the sunlight energy and convert it into glucose. Glucose is a building block of cellulose, which is used in plant cell walls. If there is more sunlight, more glucose can be made and converted into cellulose which can be made into new cell walls and when these new cells are grown at the top of the plant, its height increases. 

The Background Information may have had a lot more detail about photosynthesis and plant cell walls, but this brief summary is based on the detailed science at the start of the lab report.

Our hypothesis was correct, as the amount of sunlight increased, the height of the plants also increased. This is because there was more energy available to the plant for growth. As the amount of sunlight increases there is more energy available for photosynthesis, the chloroplasts in the plant’s leaves capture the sunlight energy and convert it into glucose. Glucose is a building block of cellulose, which is used in plant cell walls. If there is more sunlight, more glucose can be made and converted into cellulose which can be made into new cell walls and when these new cells are grown at the top of the plant, its height increases. 

This positive correlation can be seen in Graph 1, where the height increases as the amount of light increases, up to a point, where the optimum amount of light has been passed and the height of the plants remain constant. As was described in the Background Information, this is because plants also need water and CO2 to perform photosynthesis, and without increasing these control variables, increasing the  amount of light energy cannot produce further growth. This is known as the ‘law of limiting factors’ (Benney et al. 2014). In fact, increasing the amount of light further may damage the plants (BBCbitesize.com 2018), but we did not see this effect. This finding is therefore in line with the expected results as described by other researchers (Smith 2011).

Two measurements were repeated due to the values being so different to the others taken during the experiment. This was done so as not to impact the average values. However, as noted in the materials section, the intensity meter had an error of ± 1 W/m2, so although this was used to record every value, this should be taken into account. As the dependent variable measurements do not differ greatly from the averages, our findings can be seen as being reliable and the method robust enough for other people to follow and get similar results. However, the graph shows the optimum amount of sunlight may be in the range of 1200–1400 W/m2, therefore in order to provide an exact optimum value, the method could be revised to focus on this range. 

This experiment shows that as plant growth is dependent on the amount of sunlight, this finding may be of use to farmers and commercial fruit growers. In the future, experiments could be designed to calculate the optimum amount of sunlight needed to produce the biggest increase in crops. The following evaluation section looks at specific problems with the method and makes suggestions on how they could be improved.

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