Hi. How can we say when does a scatter diagram have a football shape? Do we need to look at the r (or correlation??) And if r=0.45 does this mean it isn´t footbal shape?

Question

anonymous · Answer

It would be helpful to see the scatter plot, but going off of what you said it doesn't sound linear.  My first attempt (if I were choosing which regression type on a ti 84) would be quadratic.

A correlation of .45 doesn't sound very tight to me, so if that is what you are dealing with then you might have to choose a different regression type.  Or, if that is the tightest (i.e. close to 1 or -1) you can get it, then you would just have to accept that your model won't be very accurate.