Maths PMCC values

Would a PMCC value of -0.8 be greater than a value of 0.6 because -0.8 would suggest that the values are closer together or what would it be 0.6 because its positive?

It depends what you mean by "greater". If you mean "which has the biggest linear correlation", then yes, it is the -0.8, because it is closer to -1 than 0.6 is to 1. It is of course telling you that the correlation is negative.

So if I was just asked for greater, it wouldn't make any sense?

It probably means which shows the largest correlation, but it needs to be clearer to be sure. What is the exact wording of the question?

I can't remember exactly but it showed 4 graphs and 2 of them had a positive correlation but neither were greater than about 0.6 (estimate), there was one graph that had all points in a straight line so PMCC would = 0 and another graph that had a strong negative correlation around -0.8. The Q asked which graph has the greatest PMCC value

It probably does mean the strongest linear correlation, positive or negative.

Are you sure that the graph with all the points on a straight line would have a PMCC of zero? Why?

I mean a straight line where y=x, it would have a PMCC of 0 because y would not depend on x.

Do you mean a straight line where y = constant?