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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. |
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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.
For more information... we recommend:
- WINKS -- a simple to use and affordable statistical software program that will help you analyze, interpret and write-up your results. Download a free trial copy.
- Additional statistics tutorials.
- Against All Odds VIDEOS - Now in VHS or DVD formats Teaching Videos from Annenberg/PBS Click here for info
- BeSmartNotes Reference sheets for SAS, SAS ODS, SPSS and WINKS - Click here for info.
- Statistical Analysis Quick Reference Guidebook: With SPSS Examples is a practical "cut to the chase" handbook that quickly explains the when, where, and how of statistical data analysis as it is used for real-world decision-making in a wide variety of disciplines. It contains examples using SPSS Statistics software. In this one-stop reference, the authors provide succinct guidelines for performing an analysis, avoiding pitfalls, interpreting results, and reporting outcomes. Paperback.Sage Publishers ISBN: 1412925606 Order book from Amazon
