In science, we are often interested in the relationships between different factors. If the factor that you choose to measure can take different values, it is called a variable. If another factor is not allowed to change value and instead is kept fixed at all times, it is called a controlled variable.
The school’s PE teacher is concerned that more and more students are purchasing sugary sweets, crisps and fizzy drinks from the vending machines. Word has reached the PE department that your survey was excellent. Your PE teacher asks you to design a simple investigation to see if there is a link between the energy content of the foods bought in the vending machine and the BMI of the students purchasing items from the machine.
Fig. 2.5.2 Student at vending machine
6 Design and produce a simple data collection table to record all of the key information. The answers to the following questions will help inform the design of your data collection table and how you will then collect and analyse your data:
a. What is the PE teacher’s hypothesis?
b. What three pieces of background information should you collect from each student?
c. What measurements will you need to take from each student?
d. How will you protect their anonymity?
e. How will you collect data regarding energy content of food? (Hint: all labels should quote kJ/100 g.)
f. How will you use this data to calculate BMI values?
g. What are the two variables in this investigation?
h. Were there any controlled (fixed) variables? Is this a strength or weakness of your investigation? Explain.
i. What is a control group? Would it be possible to include a control group in this investigation?
j. Can you think of any sources of error that may occur during the investigation? How might you reduce their effect?
k. Select a suitable chart that you could use to see the trend between your variables. Consider the title and labels that you will put on your chart.
l. Would you have any ethical concerns about carrying out this investigation?
