# i) data? j) Use a subset of

i) Input your data used to plot the graph into Excel and use it to draw a graph. See if you can get Excel to draw a trend line – there are various options for the general shape of the trend line and each is effectively a model of your data. Is there an appropriate option for your data?
j) Use a subset of your data (the same subset that you used in e) to plot another graph just of the section of data that crosses the x-axis. Add a straight trend line to this graph and get Excel to show you the equation for this line. Solve the equation of the line for y=0 to identify the point where the line intercepts the x-axis (the light compensation point). Compare your hand calculated equation and intercept point with the Excel derived one.
k) Your Excel generated straight trend line is a simple computer model of your data. What assumptions does this modelling make? What are the advantages and disadvantages of modelling data in this way?
l) If the experiment was left for much too long you might expect to see that all of the tubes contained either yellow or dark purple liquid but no bottles with an intermediate colour except for the control bottle. Why would this occur and what precaution