Comparing sales per hour this year, with last years.

Hey guys,

Let me explain,

Work has given me a hourly sales data for the last 2 weeks, and Last years hourly data for the equivalent 2 weeks.

The question is compare the average of the last 2 weeks against the average of the equivalent 2 weeks last year and evaluate if the trading performance is majorly different.

I have to copy the answer to use it with other sites aswell so nothing too long.

This is such an easy task, yet I cant seem to get my head around it. What formulas to use? Should I use percentages or leave it? Charts graphs are all welcome too. Please help! I want to impress!

Kennith