Struggling with statistical analysis for Biology Extended Essay Watch

TheIBFailure
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So my EE supervisor is currently competing in an international sports competition so I thought I'd ask here.
I've been told its mandatory to include a statistics test within my EE, however I am not sure what one I can use. The data I have collected is in relation to the effect of salinity on a certain type of plant. I have changed the salinity of the growth medium and measured the length of the resulting shoots.
Any help much appreciated.
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tchaikovskyed
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It doesn't actually have to be that complicated. Simple statistics like mean, median or mode & standard deviation will be accepted.
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parzi10
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You can also try using the T-Test - I found it very useful while writing my Biology EE.
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dschramm
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(Original post by TheIBFailure)
So my EE supervisor is currently competing in an international sports competition so I thought I'd ask here.
I've been told its mandatory to include a statistics test within my EE, however I am not sure what one I can use. The data I have collected is in relation to the effect of salinity on a certain type of plant. I have changed the salinity of the growth medium and measured the length of the resulting shoots.
Any help much appreciated.
I recently completed the IB program and did my EE in Biology as well!

It is highly recommended that you include a statistics test if you want to maximize your marks in the Biology Extended Essay. The statistical test that you use is going to depend on how many groups you want to compare. Because the data that you are using (length) is continuous, you would likely be using an unpaired T-Test to compare two means. This would occur if you had a control (say, 0% salinity) and "ocean water" (4% salinity). If you wanted to just compare these two together, T-Tests would be perfect.

If you're trying to compare multiple groups, (ie. there are more than two different salinities that you've created, maybe 0%, 2%, 4%, 6%, and 8%) this gets a lot trickier. You would likely be using ANOVA because it will consistently keep the confidence of the result at 95%. I used unpaired T-Tests in my extended essay, but ANOVA would have been just as good if I was comparing more than two groups. Check out the link here if you want to learn more about ANOVA.

Also, if you're comparing salinities across gradations rather than different salinity groups, you may want to use Pearson linear regression, and R-values for that. This would be if you had many different salinities each with respective stem lengths that you could plot on a graph. Typically, this would not be done in an experiment that you designed yourself.

Because there are so many statistical tests available, it's difficult to pinpoint which one is best from your question. From the sounds of it, I would recommend either unpaired T-Tests or ANOVA. Hopefully this has helped a bit in your decision!
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Tutsani
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(Original post by dschramm)
I recently completed the IB program and did my EE in Biology as well!

It is highly recommended that you include a statistics test if you want to maximize your marks in the Biology Extended Essay. The statistical test that you use is going to depend on how many groups you want to compare. Because the data that you are using (length) is continuous, you would likely be using an unpaired T-Test to compare two means. This would occur if you had a control (say, 0% salinity) and "ocean water" (4% salinity). If you wanted to just compare these two together, T-Tests would be perfect.

If you're trying to compare multiple groups, (ie. there are more than two different salinities that you've created, maybe 0%, 2%, 4%, 6%, and 8%) this gets a lot trickier. You would likely be using ANOVA because it will consistently keep the confidence of the result at 95%. I used unpaired T-Tests in my extended essay, but ANOVA would have been just as good if I was comparing more than two groups. Check out the link here if you want to learn more about ANOVA.

Also, if you're comparing salinities across gradations rather than different salinity groups, you may want to use Pearson linear regression, and R-values for that. This would be if you had many different salinities each with respective stem lengths that you could plot on a graph. Typically, this would not be done in an experiment that you designed yourself.

Because there are so many statistical tests available, it's difficult to pinpoint which one is best from your question. From the sounds of it, I would recommend either unpaired T-Tests or ANOVA. Hopefully this has helped a bit in your decision!
hi, it's been two years since you posted this but i'm doing my extended essay now and this is a huge help. Thank you!
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