What is the explanatory variable? What is the explanatory variable? Protein in grams, because it is on the horizontal axis. It is an arbitrary choice. Either variable can be considered the explanatory variable. There is not enough information to know. Price in dollars, because the price determines how much protein a person can buy. Regression Equation: Parameter Estimate Intercept 3.232 Slope (Protein (g)) 0.05717 Model Summary: Statistic Value Correlation Coefficient r 0.782 Coefficient of Determination r2 61.2% Residual Standard Deviation 0.2915 Statistics: Variable n Mean Std. Dev. Min. Q1 Median Q3 Max. Price (USD) 15 4.463 0.451 3.890 3.990 4.390 4.890 5.090 Protein (g) 15 21.53 6.17 9.00 18.50 20.00 24.50 36.00