A correlation is a way to describe the relationship between two variables. In a positive correlation, as the values of one of the variables increase, the values of the second variable also increase. In a negative correlation, as the values of one of the variables increase, the values of the second variable decrease. Or there may be no correlation between the two variables. If researchers know how two variables are correlated, they can make a prediction about one variable based on what they know about the other variable. (a) Which variable(s) is/are positively correlated with the volume of nectar production in this genus? (b) Which is/are negatively correlated? (c) Which show(s) no clear relationship?
