Are we really consuming less now?

Download this spread sheet

What to do:

• Find the linear solution by changing the slope (cell F4) and intercept parameters (cell G4) until the value in cell F7 is a minimum. (this value represents a chi^2 test of the data over the first 550 weeks of the data - the reason for that will be apparent later).

  You should be able to find a solution with chi^2 value of 10.93

• Now see if you can produce a better fit (e.g. a lower value for the number in cell F7) by adding a sine wave by adjusting the properties in cells F1,F2 and F3.

  You should be able to find a combined solution that would give you a chi^2 value of 7.72

  Can we add a third component? If so, what does it look like?

Week 10