Excercise $18-3$The owner of a convenience store near Salt Lake CIty in Utah has been tabulating weekly sales at the store, excluding gas. The

accompanying table shows a portion of the sales for $30$ weeks.

RulctureClick here for the Excel Data File

a$.$ Use the $3-$perlod moving average to forecast sales for the $31$st week. $($Do not round Intermedlate calculations. Round final answer

to $2$ decimal places.$)$

hat$(y{)}_t=$

b$.$ Use simple exponential smoothing with $=0\mathrm{.}3$ to forecast sales for the $31$st week. $($Do not round Intermedlate calculations. Round

final answer to $2$ decimal places.$)$

c$-1.$ Report the performance measures for the techniques in parts a and b$.($Do not round Intermedlate calculations. Round final

answers to $2$ decimal places.$)$

$c-2.$ Which is the preferred technique for making the forecast?

Week Sales

$15494\mathrm{.}7400$

$25632\mathrm{.}4400$

$35413\mathrm{.}1400$

$45613\mathrm{.}0600$

$55498\mathrm{.}8200$

$65610\mathrm{.}0000$

$75388\mathrm{.}6600$

$85281\mathrm{.}5600$

$94929\mathrm{.}6600$

$105113\mathrm{.}2600$

$115140\mathrm{.}8000$

$125528\mathrm{.}4000$

$135216\mathrm{.}2800$

$145177\mathrm{.}5200$

$155027\mathrm{.}5800$

$165335\mathrm{.}6200$

$175097\mathrm{.}9600$

$185018\mathrm{.}4000$

$195073\mathrm{.}4800$

$204986\mathrm{.}7800$

$215163\mathrm{.}2400$

$224821\mathrm{.}5400$

$235213\mathrm{.}2200$

$245492\mathrm{.}7000$

$255136\mathrm{.}7200$

$264965\mathrm{.}3600$

$275137\mathrm{.}7400$

$285461\mathrm{.}0800$

$295118\mathrm{.}3600$

$305310\mathrm{.}1200$