For my project I am investigate the relationship between weight, height and body mass index. I will be investigating how the body mass index

The body mass index of each year group

The body mass index of boys and girls in each year group

The comparison between body mass index and between the males and the females will show if the body mass index does depend on your gender. It also shows if the average for the males is different to the females. This will tell you if the BMI average for the males should be the same for the females.

The comparison between the body mass index and the year group shows if the body mass index should be different depending on your age. This will also show as you get older, is your BMI supposed to increase, decrease or stay the same. Another result it could show is if the correlation is stronger or weaker as you grow up.

The comparison between the males and females of each year group would show if BMI is dependant on gender and year group.

I will also be using the formula for BMI (weight in kg/ height in m2) to work out and compare the BMI for each of the students. This will give you an answer, which you use a table to show you if you are underweight-obese. This table consists of 9 different ranges. These are:

 

So, if a person were to weigh 60 kilograms, with a height of 1.6m, to work out his/her BMI you would:

 

60

1.60² = 22.03856… that would be rounded to 22. This would fall under the category of “In normal range”, for males and females.

I will be using these formulas to compare the body mass index of boys and girls and their ages. I will do this by creating a scatter graph. I will also show the information on a box-and-whisker diagram to show the spread of the data. These diagrams will be useful because it shows the data easily so it is easy to read. It also shows the data in another way where you can find the information easily.

As a result of the calculations and the diagrams I will be able to compare the BMI of students in different year groups, the BMI difference between boys and girls, and finally the comparison between boys and girls in different year groups.

My Samples:

I collected my samples by using the formula for stratified sampling to get my 119 pieces of data. In this table, you use:

(151/1183) * 119= 15

This gives you how much boys in year 7 are going to be in the sample window. Then using this amount I will pick this much from each year and gender. I will pick this number of students randomly by giving each student a random number. Then I would sort Year Group, then by Gender and finally by random number. Then using the stratified sampling I pick the first number of people depending on their size.

Males and Females:

The BMI between Males and Females is very much the same. In year 7 the difference between the box and whisker diagrams is very minimal. The females range is not as wide as the Year 7 Males, but it has a higher Median, higher upper quartile, but a lower, lower quartile. Therefore the Year 7 Females have a wider inter-quartile range.

Year 7 Females:

Range:                        11.3

Lower Quartile:        16.95

Median:                20.8

Upper Quartile:        23.2

Semi I.Q. Range:        3.125

Year 7 Males:

Range:                        12.9

Lower Quartile:        18.1

Median:                20.3

Upper Quartile:        22.6

Semi I.Q. Range:        2.25

This shows completely the opposite of my prediction because it shows that the Females’ averages are all higher than the Males.

For Year 8:

Males:

Range:                        22

Lower Quartile:        16.4

Median:                17.6

Upper Quartile:        19.3

Semi I.Q. Range:        1.45

Females:

Range:                        8.6

Lower Quartile:        17.5

Median:                19.3

Upper Quartile:        20.6

Semi I.Q. Range:        1.55

Year 8 Males has a much larger range, this may be because of a few extreme values. Every other average is lower than the Females averages.

Year 9:

Males:

Range:                        15.4

Lower Quartile:        17.7

Median:                19.75

Upper Quartile:        21.325

Semi I.Q. Range:        1.8125

Females:

Range:                        51.5

Lower Quartile:        14.9

Median:                17.45

Upper Quartile:        21.2

Semi I.Q. Range:        3.15

This shows the year 9 females have a very wide range of Body Mass Index, which may be because of an extreme value of 65.9. This is an example of unreliable data, which destroys the data in a way that it changes it mean etc… dramatically. The upper quartile is practically the same with a difference of 1.25. The median for males is much higher than the one for females. The lower quartile for males is also much higher for the males with a difference of 2.8. The most recognisable difference is the range because of the extreme value. This is one piece of data, which actually follows my prediction almost perfectly.