Exam 18: Models for Time Series and Forecasting

Gashol (a mixture of gasoline and methyl alcohol)sales in Iowa City have been recorded over the past 10 months as shown below: Manth Jan Feb Mar Apr May June Juy Aug Sep Oct Sales 75 72 81 92 90 105 112 107 110 93 -Compute the four month centered moving average.

The linear trend equation $\hat{ Y }$ = 100 + 5.2x has been developed,where $\hat{ Y }$ = estimated sales (thousands of dollars)and x = 1 for the year 1995.What level of sales would be forecast for 2012? ____________________ thousand

What is the Producer Price Index?

The larger the smoothing constant ( $\alpha$ ),the more importance is given to the actual y value for the most recent time period.

Which of the following statements is not true regarding the Consumer Price Index (CPI)?

Analysis of a time series involves identifying the components that have led to the fluctuations in the data.

In general,a moving average with a base equal to the duration of a strong cyclical or seasonal pattern will be highly useful in dampening fluctuations caused by the pattern.

Exponential smoothing requires that we assume an initial forecast value in order to get things started.

In forecasting,we use data from the ____________________ in predicting the ____________________ value of the variable of interest,such as automobile sales.

The occupancy rate for motel and hotel rooms in a small city in Michigan from 1993 to 2002 follow: 65.7 67.3 61.8 60.9 77.7 82.5 72.4 85.5 59.5 Compute a five-year moving average of the occupancy rate.

Quarterly sales The quarterly sales (in millions of dollars)of a department store chain were recorded for the years 1997-2000.They are listed below. Year Quarter Sales 1997 1 21 2 36 3 28 4 44 1998 1 25 2 23 3 39 4 36 1999 1 30 2 41 3 47 4 55 2000 1 34 2 29 3 32 4 48 -Graph the time series and the moving averages.

If you are not using a computer,it is desirable to select an even number of periods for a centered moving average unless there is some compelling reason to do otherwise.

The following trend line was calculated from quarterly data for 1995 - 1999: $\hat { y } = 0.70 + 0.005 t$ where t is 1 for the first quarter of 1995.Calculate the trend value for the second quarter of the year 2000.

The purpose of the moving average technique is to

The time series component that reflects a wavelike pattern describing a long-term trend that is generally apparent over a number of years is called:

Selecting a large value for the smoothing constant ( $\alpha$ )in exponential smoothing

Given the following units of insulated caps from 1993 to 2000,compute the exponentially smoothed series with $\alpha$ = 0.3.The data values are 90,105,126,101,107,103,79,80.

What is the Durbin-Watson test for autocorrelation,and how can it be useful in evaluating the relevance of a given regression model that has been fitted to a set of time series data?

Gashol (a mixture of gasoline and methyl alcohol)sales in Iowa City have been recorded over the past 10 months as shown below: Manth Jan Feb Mar Apr May June Juy Aug Sep Oct Sales 75 72 81 92 90 105 112 107 110 93 -Compute the exponentially smoothed sales with $\alpha$ = 0.4 and $\alpha$ = 0.8 .

We calculate the three-period moving average for a time series for all time periods except the: