In Exercises 27 38, a. Rewrite the equation in a rotated without an -term. Use the appropriate rotation formulas from Exercises 15 26. b. Express the equation involving and in the standard form of a conic section. c. Use the rotated system to graph the equation

MGSC 395 MW 5:30 Monday, March 21, 2016 Time series models (all models are wrong. Accept it. We want to figure out how wrong are they) o Graph with time as x and demand quantity as y o Your data can show as horizontal, a trend (diagonal up or down), cyclical (wave shape), or seasonality (horizontal then spike) o E t D --tF (trror at time t = actual demand minus forecasted demand) o Get the sum (∑ CFE= cumulative forecast error) and the average (x bar = average bias) To get rid of the negative signs in the errors, take the absolute value. Then x bar is MAD (mean absolute value) Or you can square the error. Then x bar is MSE