$($Forecasting$)$ The following data are monthly sales of jeans at a local department store. The buyer would like to forecast sales of jeans for the next month, July.

a$)$ Forecast sales of jeans from March to July using the two$-$period moving average $($i$.$e$.,$ n$=2),$

and forecast sales of jeans from April to July using the three$-$period moving average $($i$.$e$.,$

n$=3).$

b$)$ Compare the results in a$)$ in terms of accuracy measure$($s$).$ Which forecasting method

would you choose? why?

Month

January February March April May June

Sales

$45$

$30$

$40$

$50$

$55$

$47$