fail assumptions

Hi guys, I am testing the normally distributed errors assumptions for multiple regression with a visual inspection using a P-Plot plot. Now, I have the suspicion that the errors are not normally distributed (see image below). I have two questions about this: Is there any way to test this...

Hi all, i have a Before-After-Control-Treatment (2x2) design, resulting in two independent groups of scale data (samples in two water streams, in one a treatment has been installed at some point, both streams (two physical different locations) were sampled before and after at various occasions)...

Hi, I've been working on a little project. Last year I delivered pizzas. I recorded data for 300 of my deliveries like tip amounts, order totals, and delivery times. I have a few hypotheses I would like to test. For example, after examining the data I've noticed that the average tip from...