IB Math SL type II Portfolio - Body Mass Index

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Body Mass Index

Escaan International School



In this investigation, I will analyse various functions using the data given. A model function will be reached in base with this real-life example:

Body mass index (BMI) is a measure of one’s body fat. It is calculated by taking one’s weight (kg) and dividing it by the square of one’s height (m).

The table below provides the median BMI for females of varying ages in the US in the year 2000.


(Source: http://www.cdc.gov)

When graphed:

The independant variable is the age of the women <x>, and the dependant variable is the BMI of these women <y>. Both values have to be >0.

The behaviour of this graph can be modelled by the sine function

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, or by the cosine function

 as it is periodic and ondulating, which means it repeats a pattern as it goes up and down. Other functions can’t be used in this model as the information given can be reflected in other type of graphs. Finally, we can deduce that it will be a cosine function as the portion that we observe in tha graph doesn’t go through the origin (0,0), as the sine function would do.

After deducing which function type best fits the provided data, I used a GDC to test different forms of ...

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