Dan's grandmother gave him $30 for his birthday. He decides to put $20 in a box for saving. Every week his parents give him $5 f
or his allowance. He decides to start adding $4 of his allowance to the box every week. What is the regression line for predicting the amount of money (ŷ) that will be in his box from x weeks of adding to the box?
Let the regresssion line be linear because of a constant amount of money coming in. Let y be the total amount of money in the box and x the weeks of adding to the box:
We know that he puts $20 in the box from his birthday and $4 every week for x weeks. Therefore the total amount of money will be:
Think of a imaginary 1(-1 because of the sign) in front of the parenthesis and distribute it to the other number and so x will become -x, 3y will become -3y and -z will become z because two negatives make a positive.