2019 Year 12 IB Extended Essays

Uncertainties and error:

Graph 1 demonstrates that the plants grown in 0M and 0.0068M NaCl grew at similar rates, with the plant grown in 0.0068M NaCl having grown 0.18cm taller by day 20 when compared to the plant grown in 0M NaCl. The standard deviation of the plant in the 0M NaCl however was 1.32 which caused the error bar to overlap the height of the plant in 0.0068M in Graph 1, indicating the possibility that that the plants grown in 0M solution may have grown taller than the ones in 0.0068M. This makes concluding that low levels of salinity don’t have a significant negative impact on the growth of the plant difficult but as the height of the plants grown in the 0.0068M NaCl was constantly taller than that of the plant grown in the 0M solution, can be assumed that the 0.0068M solution had a positive impact on the growth of the plant. But on the other hand, there was a significant difference between the heights of the plants grown in 0M of NaNO3 and 0.0068M of NaNO3 with the 0M NaNO3 plant growing to 13.5cm and the 0.0068M plant growing to 16.6cm in Day 20. This implies that the positive impact of Nitrates on plant growth is substantial. From Tables 15 and 16, it can also be seen that the Standard Deviation is large for all the data except NaNO3 at a concentration of 0.1095M and NaCl at 0.0274M and 0.1095M as most of their standard deviation is less than 1. This indicates that the data collected was highly varied when determining the mean. But as the experiment is dealing with plants, a relatively large variance is expected as there are many uncontrolled variables such as seed thickness, volume of endosperm and root growth depth that could affect the values.

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