Adding a New Column Based on Statistcis to a DataFrame

this is my first question. I want to build a statistical model. I have a data and I want to add a column to this dataframe. I want this column to show some statistical things. For example my dataframe is like this

DataFrame

For example, I want to add a new column. I want this column to show "car red girl"s D value is more than the mean of all car's D. How should I do this? Which way should I use to do this statistical model. I have a large data and I can't calculate the all car's or bike's mean manually. I need a function with if-else statements and adding a column to describe is the row's D more or less than mean.