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Server date: May 18, 2008, 3:00 am
Note: these SMP calculations are always applied to the untransformed and undifferenced (original) time series.
SMP of Airline.ds
L = 1, d = D = 0
Section
Mean(k)
SE(k)
1
126.6667
13.7201
2
139.6667
19.0708
3
170.1667
18.4383
4
197
22.9664
5
225
28.4669
6
238.9167
34.9245
7
284
42.1405
8
328.25
47.8618
9
368.4167
57.8909
10
381
64.5305
11
428.3333
69.8301
12
476.1667
77.7371
Regression: S.E.(k) = alpha + beta * Mean(k)
alpha
-11.403254142558
beta
0.18861339889948
S.E.
0.0065773318024468
T-Stat
28.676278552546
The above regression result suggests that a relationship exists between the mean level and the standard error of this time series.
AI Conclusion: A Box-Cox transform is likely to induce stationarity of variance.
From this analysis it can be concluded that the time series under investigation should be transformed according to the Box-Cox transformation with lambda = -0.31. For the sake of convenience we apply lambda = 0.
To cite Wessa.net in publications use: Wessa, P. (2008), Free Statistics Software, Office for Research Development and Education, version 1.1.22-r6, URL http://www.wessa.net/
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