Extracting (Interpolating) corresponding value from a table/graph.

Hi,

I have 2 set of values, say x = {1,2,3,4,5,6,7} and y = {10.5,12,15,17.5,20,23,25.5}, using which I have drawn a standard line chart.
My question: Can I use a formula that can interpolate values for x, say what will be corresponding y when x = 2.2 or 6.5 etc etc?

Thanks in advance.