Bio-Stats question: Save the residuals from the regression of DNA concentration on phytopigment concentration . Examine the residuals to see how well the conditions for regression inference are met.

Plot the residuals against phytopigment concentration (the explanatory variable), using vertical limits −1 to 1 to make the pattern clearer. Add a horizontal line at height 0 to represent the regression line. What do you conclude about the conditions of linear relationship and constant standard deviation?

Make a histogram of the residuals. What do you conclude about Normality?