Maths IA - Do you have to explain each step in equations such as Pearson's

[udawn]

Hi!

The Maths teachers in our school said for SL IA's, we could base our IA's on statistics and use formulas like Pearson's and Spearman's and Chi-squared (not in the SL curriculum but is in Maths Studies). However, they said we have to explain the steps of each equation, as in like why do you need to multiply d^2 by 6 in Spearman's rank.

 

Is this really necessary for a 7? If so, how would you get sources like this that explain how equations are derived?

 

Thank you!

[IB Math Helper]

For mathematics that is in the curriculum such as Pearson's correlation, you do not have to explain the derivation behind them. For the Pearson's case, showing the linear regression graph accompanied by the correlation coefficient (r) and it's meaning (e.g. strong negative correlation between the two variables) would be sufficient.

However for mathematics that is not obvious or not in the curriculum, the derivation (or meaning) should be explained. For instance, going back to the Pearson's correlation coefficient (r), there is something known as the co-efficient of determination which is the square of the correlation co-efficient (r^2) and helps explain how well the model fits the data. If r= -0.9, for example, then the co-efficient of determination is r^2 = 0.81. This means that the linear regression model helps explain 81% of the data and the other 19% is explained by random error (or other variables not explained by the model). I would probably find a source for the co-efficient of determination and then explain its meaning and relevance within the context of the exploration.

Going back to your question, you'll have to explain what the Spearman's rank is and how it is derived. The clearer the explanation, the more in-depth knowledge you demonstrate. To find sources, go to the Spearman's rank correlation wiki page and look at the bottom of the page where it cites its own references. Consult those referenced books or articles and then make your own citations.

Finally, to get a 7 does not just require the math. You can have the most succinct and clearest explanations for the new mathematics you are using but this only means that you'll do well in Criterion E (Mathematical Understanding) which is worth 6 points out of a maximum of 20 for the whole exploration. To get a 7 make sure you focus on the Criterion C (Personal Engagement) and Criterion D (Critical Reflection).

[udawn]

12 hours ago, IB Math Helper said:

For mathematics that is in the curriculum such as Pearson's correlation, you do not have to explain the derivation behind them. For the Pearson's case, showing the linear regression graph accompanied by the correlation coefficient (r) and it's meaning (e.g. strong negative correlation between the two variables) would be sufficient.

However for mathematics that is not obvious or not in the curriculum, the derivation (or meaning) should be explained. For instance, going back to the Pearson's correlation coefficient (r), there is something known as the co-efficient of determination which is the square of the correlation co-efficient (r^2) and helps explain how well the model fits the data. If r= -0.9, for example, then the co-efficient of determination is r^2 = 0.81. This means that the linear regression model helps explain 81% of the data and the other 19% is explained by random error (or other variables not explained by the model). I would probably find a source for the co-efficient of determination and then explain its meaning and relevance within the context of the exploration.

Going back to your question, you'll have to explain what the Spearman's rank is and how it is derived. The clearer the explanation, the more in-depth knowledge you demonstrate. To find sources, go to the Spearman's rank correlation wiki page and look at the bottom of the page where it cites its own references. Consult those referenced books or articles and then make your own citations.

Finally, to get a 7 does not just require the math. You can have the most succinct and clearest explanations for the new mathematics you are using but this only means that you'll do well in Criterion E (Mathematical Understanding) which is worth 6 points out of a maximum of 20 for the whole exploration. To get a 7 make sure you focus on the Criterion C (Personal Engagement) and Criterion D (Critical Reflection).

Thank you so much for your help! Wait so i don't have to explain why Spearman's rank formula works, but the results from using the formula right?