A researcher wanted to build up a model to predict the yearly population size of certain species of mice in a mountainous area based on a set of environmental variables, including human population density, coverage of bamboo (a major food source for mice in the area), annual rain precipitation, and length of summer (the breeding period for mice in the area). She had the data from the past n = 30 years. For the i year, the mouse population size (y_i , in thousands), human population density (x_i1 ), bamboo coverage (x_i2 ), rain precipitation (x_i3 ), and length of summer (x_i4 , in days) were recorded.

What assumption(s) can be checked using this same Externally Studentized Residuals vs. Predicted plot? (Check all that apply.) Residuals are normally distributed O Residuals have constant variance Residauls are independent Residauls have mean of 0