A quadratic function can be drawn as a parabola on a graph. Find out how to plot the graph in this Bitesize KS3 maths video.

But how do you come up with a function to fit data? The basic idea is to create a quadratic function and vary the parameters such that the deviation of the actual data from the function is minimized.

You can make a bar graph in Excel by first selecting the range you want to depict, and then using the dropdown menu to select the desired chart.