a correlation is a way to describe the relationship between two variables. in a positive correlation, as the values of one variable increase, the values of the second variable also increase. in a negative correlation, as the values of one variable increase, the values of the second variable decrease. or there may be no correlation between 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. click on the table to see the data the researchers collected for each mimulus species. which variables are positively correlated with the volume of nectar production in this genus? select all that apply.