# Observations of the demand for a spare part stocked at a parts supply

EMIS 8348 Homework Assignment 1

Problem 1:

Observations of the demand for a spare part stocked at a parts supply depot during the

calendar year 2012 were

Month  Demand  Month  Demand

January  95  July  234

February  62  August  284

March  135  September 221

April  211  October  281

May  199  November 192

June  276  December 302

a. Determine the one-step-ahead forecasts for the demand for January 2013 using 3-,

6-, and 12-month moving averages.

b. Using a four-month moving average, determine the one-step-ahead forecasts for

July through December 2012.

c. Compute MAD, MSE, MAPE for the forecasts obtained in b.

Problem 2:

Observed weekly sales of ball peen hammers at the town hardware store over a ten-week

period have been 13, 11, 26, 21, 32, 13, 21, 22, 30, and 26.

a. Suppose that five-week moving averages are used to forecast sales. Determine the

one-step-ahead forecasts for weeks 6 through 10.

b. Suppose that exponential smoothing is used with a smoothing constant of α =

0.15. Find the exponential smoothing forecasts for weeks 6 through 10 (start the

forecasting process from week 1).

c. Based on the MAD, which forecast method is better?

Problem 3:

The sales of a tablet computer in a popular electronic store during the calendar year 2012

were

Month  Demand  Month  Demand

January  103  July  199

February  119  August  208

March  131  September 221

April  149  October  237

May  172  November 252

June  184  December 268

a. Using 3-month simple moving average and exponential smoothing (with α = 0.10

and 0.20), determine the one-step-ahead forecasts for July 2012 through January

2013.

EMIS 8348 Homework Assignment 1

b. Using 3-month double moving average (using base level and trend), determine the

one-step-ahead forecasts for July 2012 through January 2013.

c. Compute MAD, MSE, and MAPE for the above forecasts.

d. Based on the MAPE, which forecast method is the best?

Problem 4:

Compile a list of major system life-cycle activities. For each activity on the list, try to

find the related supply chain activities. Present your finding in a table with the system

life-cycle stage in the first column, system life-cycle activities in the second column and

the related supply chain activities in the third column.