One explanation for this would be that girls do not have as big a growth spurt when they hit puberty compared to that of the average boy.
Hypothesis 2
The second hypothesis was that in year 7 girls weigh more than boys however by year 11 boys weigh more than girls. My first attempt to prove this is to find the mean of weights. The results showed me that the girls in year 7 weigh 1 kg more than the boys and by year 11 the boys weigh 16 kg more than the girls. Although the difference between the year 7’s is slight it is still true to my hypothesis and the difference between year 11’s supports my hypothesis fully. The investigation into mean weights has shown me that my hypothesis may be correct however I still need to investigate further.
I next looked at the Standard Deviation of weights. The S.D’s showed me again that the girls and boys weights in year 7 are similar, the bys being 2 kg less than the girls, however by year 11 the boys weigh more than girls with a difference of around 5 kg. This slightly disproves the first part of my hypothesis, that girls weigh more than boys in year 7 however does help me to prove that by year 11 boys do weigh more than girls.
To further test my hypothesis I created box and whicker plots from cumulative frequency curves. This showed me that year 7 girls and boys have a similar spread of weights however 75% of year 11 boys are taller than 75% of the girls.
These findings help prove that in year 11 boys weigh more than girls but the first part of my hypothesis has been disproved to some extent. Most of my investigation indicates that year 7 boys weigh more than year 7 girls however more investigation would need to be carried out to make this conclusive.
Hypothesis 3
My third hypothesis was that in year 7 there is no link between height in weight however by year 11 the taller you are the more you will weigh. To test this hypothesis I plotted scatter diagrams of heights and weights for both genders and years. In year 7 boys my scatter diagram does show me a slight positive correlation this does not agree with my hypothesis. However in year 7 girls here is no correlation. Looking at the year 11 boys there is a very obvious positive correlation. The year 11 girls also show some positive correlation. This goes some way to proving the second part of my hypothesis however the findings for the year 7’s is inconclusive.
I then used Spearman’s Rank to tell me how much of a correlation between heights and weights in year 7 and 11. Year 7 boys do show a high correlation between height and weight, whilst girls show little correlation however the year 11’s both show a higher correlation, boys have 0.9 and girls 0.5. This does go against the first part of my hypothesis but does support the idea that a greater link between height and weight is present in year 11. I believe that the first part of my hypothesis has been disproved however there isn’t a correlation between height and weight in year 7 girls. The second part of my hypothesis has been proved.
Evaluation
Overall I have been pleased with how my investigation has panned out. Most of my hypotheses have been proved correct, however I do believe that my investigation could have been more conclusive. The best way to achieve this would be to either study all year groups or collect a larger sample of students. Both of these would have led me to find a greater accuracy and depth within my discoveries.
