Forecasting 1, del 2

Question 1

Explain trend projection

Answer 1

Trend projection can be used if a time series exhibits a linear trend. In that case, the method of least squares* is used. Försöker förlänga trenden in i framtiden.

Question 2

Vad innebär least squares?

Answer 2

Least squares determine the unique trend line forecast. It minimizes the mean square error between the trend line forecasts and the actual observed values for the time series. (Used in regression analysis

Question 3

Vad är formeln för trend projection?

Answer 3

Tt = b0 + b1*t

Question 4

Vad står Tt, b1, b0 för?

Answer 4

Tt = trend forecast for time period t

b1= slope of the trend line

b0 = trend line projection for time 0

Question 5

Formel för b0

Answer 5

b0 = Y_bar - b1*t_bar

Question 6

Formel för b1

Answer 6

n*summa tY - summa t * summa Y / n * summa t^2 - (summa t)^2

Question 7

Vad står Yt, Y_bar, t_bar för?

Answer 7

Yt = observed value of the time series at time period t

Y_bar = average of the observed values for Yt

t_bar = average time period for the n observations