In the Fingers data frame, you can see that the mean thumb length of males is 6.447 mm longer than the mean thumb length of females: b1 ( Thumb ~ Sex, data = Fingers) Im (Thumb ~ Sex, data = Fingers) 6.44681845238095 Call: Im( formula = Thumb ~ Sex, data = Fingers) Coefficients : (Intercept) Sexmale 58 . 256 6.447 What does the following line of code do? b1(Thumb ~ shuffle(Sex), data = Fingers) [ Select ] This will give you the same result every time you run this line of code. [ Select ] This will give you a different result every time you run it. [ Select ] This simulates a DGP/population where the difference between mean thumb lengths of males and females is 6.447. [ Select ] This simulates a DGP/population where the difference between mean thumb lengths of males and females is zero