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These WINKS statistics tutorials explain the use and interpretation of standard statistical analysis techniques for Medical, Pharmaceutical, Clinical Trials, Marketing or Scientific Research. The examples include how-to instructions for WINKS SDA Version 6.0 Software. Download evaluation copy of WINKS.

This tutorial illustrates how to model parameters for an ARMA Time Series and to create a forecast using WINKS SDA (Version 6.09 and later)

Estimate Parameters

Step 1: Open the time series data file. For this example, open SUN.SDA.

Step 2: Select Analyze -> Time Series -> Model Data. Select COUNT as the variable to analyze.

Step 3: In the dialog box section titled “Model the Data” enter a 3 in the “P” text box to specify that you want to model the data as an ARMA(3,0), and click Calculate.

The following information is reported:

Series Length =  176

Estimated parameters for P = 3 and Q = 0

Burg/Tiao/Tsay AR Estimates

---------------------------

Estimated Burg/Tiao/Tsay AR Parameters:

1) 1.266145           2) -0.498998

3) -0.112711

White Noise Variance  = 232.8768

AIC                   = 965.2897

AR Factors for Burg-Tsay Estimates

ROOT              ABS RECIP    FREQUENCY  OPERATOR COEFS

.9860 ± .6436i    0.8493       0.0920     1 - 1.422B + 0.721B^2

-6.3993           0.1563       0.5000     1 + 0.156B

Step 4: Click “Data View” to see the results – which includes spectrum and residuals.

Forecast

Once you have the estimates of a model, you can use this information to create a forecast. SDA will allow you to use your model to forecast future values of the series. An optional 95% confidence bound may be plotted for your estimated forecast.

Step 5: Select Analyze -> Time Series -> Forecast. Choose COUNT as the variable to forecast. The following dialog box appears:

At the bottom of the dialog box, select how you want to forecast. In this case select “Beyond Series N= 20.” Click Calculate. A forecast summary is reported for the model indicated.

Forecast data is based on the following information

Forecast 20 steps beyond series.

Series Length =  176

Differenced =  0

Estimated parameters for p = 3 and q = 0

AR Parameters:

1) 1.266145           2) -0.498998

3) -0.112711

Estimated WNV =  232.876837617018

Forecast Summary...

COUNT       LOWER       UPPER      FORECAST     SERIES         PSI

1         80.9        80.9        80.9        80.9      1.2661

2         83.4        83.4        83.4        83.4      1.1041

3         47.7        47.7        47.7        47.7      0.6535

4         47.8        47.8        47.8        47.8      0.1337

5         30.7        30.7        30.7        30.7     -0.2812

Step 6: Click on “Data View.” The WINKS Data sheet contains columns for the forecast and upper and lower confidence levels.

Step 7: To plot the results, select Graph/Charts -> Line/Time Series Plots -> Overlay. Specify Lower, Upper and Forecast (in that order) to plot. The following plot appears indicating the original data, a forecast, and upper and lower limits for the forecast.

This procedure is available in the WINKS Professional edition.

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