We are tasked to build a linear model to predict the current of the river based on river width, river depth, distance to the ocean and bank height in order to understand the variation in stream velocity (current). It also says to verify if there are any interaction effects.
As a beginner, what I was just thinking of doing is to make an additive/main effect model to see which of the four variables are significant:
current ~ width+depth+oceandistance+bankheight)
And then eventually do an interaction effect model to see if there are any significant interactions.
current ~ width*depth*oceandistance*bankheight)
I haven't tried anything but I'm not sure if this is the best way to do it. I've heard about stepwise reduction as well but I'm not quite sure how and when to use it.