When two variables move in the same direction, the curve relating them isupward sloping, and we say the variables are positively related. upward sloping, and we say the variables are negatively related. downward sloping, and we say the variables are positively related. downward sloping, and we say the variables are negatively related?

When two variables move in the same direction, the curve relating them is upward sloping, and we say the variables are positively related. 

Refer to the attached graph for an explanation. Here we have the measure of armspan on the X-axis and height on the Y-axis.

The graph is upward sloping because as the measurement of armspan increases (on the X-axis), so does the measurement of height (on the Y-axis). Therefore, it can be said that armspan and height are positively related as an increase in one of them results in an increase in the other.